Changelog — Python 3.7.1 documentation

# Changelog

## Python next

Release date: XXXX-XX-XX

### Security

- bpo-34791: The xml.sax and xml.dom.domreg no longer use environment variables to override parser implementations when sys.flags.ignore_environment is set by -E or -I arguments.

### Core and Builtins

- bpo-35214: Fixed an out of bounds memory access when parsing a truncated unicode escape sequence at the end of a string such as `'\N'`. It would read one byte beyond the end of the memory allocation.
- bpo-35214: The interpreter and extension modules have had annotations added so that they work properly under clang’s Memory Sanitizer. A new configure flag –with-memory-sanitizer has been added to make test builds of this nature easier to perform.
- bpo-35193: Fix an off by one error in the bytecode peephole optimizer where it could read bytes beyond the end of bounds of an array when removing unreachable code. This bug was present in every release of Python 3.6 and 3.7 until now.
- bpo-29341: Clarify in the docstrings of `os` methods that path-like objects are also accepted as input parameters.
- bpo-34974: `bytes` and `bytearray` constructors no longer convert unexpected exceptions (e.g. `MemoryError` and `KeyboardInterrupt`) to `TypeError`.
- bpo-34973: Fixed crash in `bytes()` when the `list` argument is mutated while it is iterated.
- bpo-34824: Fix a possible null pointer dereference in Modules/_ssl.c. Patch by Zackery Spytz.
- bpo-1621: Do not assume signed integer overflow behavior (C undefined behavior) when performing set hash table resizing.

### Library

- bpo-35062: Fix incorrect parsing of `_io.IncrementalNewlineDecoder`’s translate argument.
- bpo-35079: Improve difflib.SequenceManager.get_matching_blocks doc by adding ‘non-overlapping’ and changing ‘!=’ to ‘<’.
- bpo-35017: `socketserver.BaseServer.serve_forever()` now exits immediately if it’s `shutdown()` method is called while it is polling for new events.
- bpo-31047: Fix `ntpath.abspath` regression where it didn’t remove a trailing separator on Windows. Patch by Tim Graham.
- bpo-34794: Fixed a leak in Tkinter when pass the Python wrapper around Tcl_Obj back to Tcl/Tk.
- bpo-35008: Fixed references leaks when call the `__setstate__()` method of `xml.etree.ElementTree.Element` in the C implementation for already initialized element.
- bpo-23420: Verify the value for the parameter ‘-s’ of the cProfile CLI. Patch by Robert Kuska
- bpo-33947: dataclasses now handle recursive reprs without raising RecursionError.
- bpo-16965: The 2to3 `execfile` fixer now opens the file with mode `'rb'`. Patch by Zackery Spytz.
- bpo-34966: `pydoc` now supports aliases not only to methods defined in the end class, but also to inherited methods. The docstring is not duplicated for aliases.
- bpo-34941: Methods `find()`, `findtext()` and `findall()` of the `Element` class in the `xml.etree.ElementTree` module are now able to find children which are instances of `Element` subclasses.
- bpo-34936: Fix `TclError` in `tkinter.Spinbox.selection_element()`. Patch by Juliette Monsel.
- bpo-34866: Adding `max_num_fields` to `cgi.FieldStorage` to make DOS attacks harder by limiting the number of `MiniFieldStorage` objects created by `FieldStorage`.
- bpo-34536: `Enum._missing_`: raise `ValueError` if None returned and `TypeError` if non-member is returned.
- bpo-34574: OrderedDict iterators are not exhausted during pickling anymore. Patch by Sergey Fedoseev.

### Documentation

- bpo-35089: Remove mention of `typing.io` and `typing.re`. Their types should be imported from `typing` directly.
- bpo-35038: Fix the documentation about an unexisting `f_restricted` attribute in the frame object. Patch by Stéphane Wirtel
- bpo-35044: Fix the documentation with the role `exc` for the appropriated exception. Patch by Stéphane Wirtel
- bpo-34967: Use app.add_object_type() instead of the deprecated Sphinx function app.description_unit()
- bpo-11233: Create availability directive for documentation. Original patch by Georg Brandl.
- bpo-33594: Document `getargspec`, `from_function` and `from_builtin` as deprecated in their respective docstring, and include version since deprecation in DeprecationWarning message.
- bpo-32613: Update the faq/windows.html to use the py command from PEP 397 instead of python.

### Tests

- bpo-21263: After several reports that test_gdb does not work properly on macOS and since gdb is not shipped by default anymore, test_gdb is now skipped on macOS when LLVM Clang has been used to compile Python. Patch by Lysandros Nikolaou

### Build

- bpo-35139: Fix a compiler error when statically linking `pyexpat` in `Modules/Setup`.
- bpo-35011: Restores the use of pyexpatns.h to isolate our embedded copy of the expat C library so that its symbols do not conflict at link or dynamic loading time with an embedding application or other extension modules with their own version of libexpat.
- bpo-28015: Have –with-lto works correctly with clang.

### Windows

- bpo-35067: Remove _distutils_findvs module and use vswhere.exe instead.
- bpo-32890: Fix usage of GetLastError() instead of errno in os.execve() and os.truncate().

### macOS

- bpo-35025: Properly guard the use of the `CLOCK_GETTIME` et al. macros in `timemodule` on macOS.
- bpo-24658: On macOS, fix reading from and writing into a file with a size larger than 2 GiB.

### IDLE

- bpo-35213: Where appropriate, use ‘macOS’ in idlelib.
- bpo-34864: Document two IDLE on MacOS issues. The System Preferences Dock “prefer tabs always” setting disables some IDLE features. Menus are a bit different than as described for Windows and Linux.
- bpo-35202: Remove unused imports from lib/idlelib
- bpo-33000: Document that IDLE’s shell has no line limit. A program that runs indefinitely can overfill memory.
- bpo-23220: Explain how IDLE’s Shell displays output.
- bpo-35099: Improve the doc about IDLE running user code. The section is renamed from “IDLE – console differences” is renamed “Running user code”. It mostly covers the implications of using custom sys.stdxxx objects.
- bpo-35097: Add IDLE doc subsection explaining editor windows. Topics include opening, title and status bar, .py* extension, and running.
- bpo-35093: Document the IDLE document viewer in the IDLE doc. Add a paragraph in “Help and preferences”, “Help sources” subsection.
- bpo-35088: Update idlelib.help.copy_string docstring. We now use git and backporting instead of hg and forward merging.
- bpo-35087: Update idlelib help files for the current doc build. The main change is the elimination of chapter-section numbers.

### Tools/Demos

- bpo-34989: python-gdb.py now handles errors on computing the line number of a Python frame.

## Python 3.7.1 final

Release date: 2018-10-20

### Library

- bpo-34970: Protect tasks weak set manipulation in `asyncio.all_tasks()`

## Python 3.7.1 release candidate 2

Release date: 2018-10-13

### Core and Builtins

- bpo-34879: Fix a possible null pointer dereference in bytesobject.c. Patch by Zackery Spytz.
- bpo-34854: Fixed a crash in compiling string annotations containing a lambda with a keyword-only argument that doesn’t have a default value.
- bpo-34320: Fix `dict(od)` didn’t copy iteration order of OrderedDict.

### Library

- bpo-34769: Fix for async generators not finalizing when event loop is in debug mode and garbage collector runs in another thread.
- bpo-34922: Fixed integer overflow in the `digest()` and `hexdigest()` methods for the SHAKE algorithm in the `hashlib` module.
- bpo-34909: Enum: fix grandchildren subclassing when parent mixed with concrete data types.
- bpo-34900: Fixed `unittest.TestCase.debug()` when used to call test methods with subtests. Patch by Bruno Oliveira.
- bpo-34871: Fix inspect module polluted `sys.modules` when parsing `__text_signature__` of callable.
- bpo-34872: Fix self-cancellation in C implementation of asyncio.Task
- bpo-34819: Use a monotonic clock to compute timeouts in `Executor.map()` and `as_completed()`, in order to prevent timeouts from deviating when the system clock is adjusted.
- bpo-34521: Use `socket.CMSG_SPACE()` to calculate ancillary data size instead of `socket.CMSG_LEN()` in `multiprocessing.reduction.recvfds()` as RFC 3542 requires the use of the former for portable applications.
- bpo-34334: In `QueueHandler`, clear `exc_text` from `LogRecord` to prevent traceback from being written twice.
- bpo-6721: Acquire the logging module’s commonly used internal locks while fork()ing to avoid deadlocks in the child process.
- bpo-34172: Fix a reference issue inside multiprocessing.Pool that caused the pool to remain alive if it was deleted without being closed or terminated explicitly.

### Documentation

- bpo-32174: chm document displays non-ASCII charaters properly on some MBCS Windows systems.

### Tests

- bpo-32962: Fixed test_gdb when Python is compiled with flags -mcet -fcf-protection -O0.

### macOS

- bpo-34370: Revert to using the released Tk 8.6.8 with macOS installers instead of the Tk 8.6.x development snapshot used with 3.7.1rc1 and 3.6.7rc1. The snapshot introduced at least one significant regression (bpo-34927).

### C API

- bpo-34910: Ensure that `PyObject_Print()` always returns `-1` on error. Patch by Zackery Spytz.

## Python 3.7.1 release candidate 1

Release date: 2018-09-26

### Security

- bpo-17239: The xml.sax and xml.dom.minidom parsers no longer processes external entities by default. External DTD and ENTITY declarations no longer load files or create network connections.
- bpo-34623: CVE-2018-14647: The C accelerated _elementtree module now initializes hash randomization salt from _Py_HashSecret instead of libexpat’s default CSPRNG.
- bpo-34405: Updated to OpenSSL 1.1.0i for Windows builds.
- bpo-33871: Fixed sending the part of the file in `os.sendfile()` on macOS. Using the trailers argument could cause sending more bytes from the input file than was specified.
- bpo-32533: Fixed thread-safety of error handling in _ssl.

### Core and Builtins

- bpo-34783: Fix a crash with musl libc (on Alpine Linux) when the script filename specified on the command line doesn’t exist.
- bpo-34762: Fix contextvars C API to use PyObject* pointer types.
- bpo-34735: Fix a memory leak in Modules/timemodule.c. Patch by Zackery Spytz.
- bpo-34588: Fix an off-by-one in the recursive call pruning feature of traceback formatting.
- bpo-34485: Standard streams like sys.stdout now use the “surrogateescape” error handler, instead of “strict”, on the POSIX locale (when the C locale is not coerced and the UTF-8 Mode is disabled).
- bpo-34485: Fix the error handler of standard streams like sys.stdout: PYTHONIOENCODING=”:” is now ignored instead of setting the error handler to “strict”.
- bpo-34527: On FreeBSD, Py_DecodeLocale() and Py_EncodeLocale() now also forces the ASCII encoding if the LC_CTYPE locale is “POSIX”, not only if the LC_CTYPE locale is “C”.
- bpo-34527: The UTF-8 Mode is now also enabled by the “POSIX” locale, not only by the “C” locale.
- bpo-34400: Fix undefined behavior in parsetok.c. Patch by Zackery Spytz.
- bpo-34377: Update valgrind suppression list to use `_PyObject_Free`/`_PyObject_Realloc` instead of `PyObject_Free`/`PyObject_Realloc`.
- bpo-34170: -X dev: it is now possible to override the memory allocator using PYTHONMALLOC even if the developer mode is enabled.
- bpo-34126: Fix crashes when profiling certain invalid calls of unbound methods. Patch by Jeroen Demeyer.
- bpo-24618: Fixed reading invalid memory when create the code object with too small varnames tuple or too large argument counts.
- bpo-34068: In `io.IOBase.close()`, ensure that the `closed` attribute is not set with a live exception. Patch by Zackery Spytz and Serhiy Storchaka.
- bpo-34087: Fix buffer overflow while converting unicode to numeric values.
- bpo-34080: Fixed a memory leak in the compiler when it raised some uncommon errors during tokenizing.
- bpo-34066: Disabled interruption by Ctrl-C between calling `open()` and entering a with block in `with open()`.
- bpo-34042: Fix dict.copy() to maintain correct total refcount (as reported by sys.gettotalrefcount()).
- bpo-33985: Implement contextvars.ContextVar.name attribute.
- bpo-33956: Update vendored Expat library copy to version 2.2.5.
- bpo-24596: Decref the module object in `PyRun_SimpleFileExFlags()` before calling `PyErr_Print()`. Patch by Zackery Spytz.
- bpo-33451: Close directly executed pyc files before calling `PyEval_EvalCode()`.
- bpo-33824: Fix “LC_ALL=C python3.7 -V”: reset properly the command line parser when the encoding changes after reading the Python configuration.
- bpo-25750: Fix rare Python crash due to bad refcounting in `type_getattro()` if a descriptor deletes itself from the class. Patch by Jeroen Demeyer.
- bpo-31902: Fix the `col_offset` attribute for ast nodes `ast.AsyncFor`, `ast.AsyncFunctionDef`, and `ast.AsyncWith`. Previously, `col_offset` pointed to the keyword after `async`.
- bpo-25862: Fix assertion failures in the `tell()` method of `io.TextIOWrapper`. Patch by Zackery Spytz.
- bpo-31577: Fix a crash in `os.utime()` in case of a bad ns argument. Patch by Oren Milman.

### Library

- bpo-29577: Support multiple mixin classes when creating Enums.
- bpo-34670: Add SSLContext.post_handshake_auth and SSLSocket.verify_client_post_handshake for TLS 1.3’s post handshake authentication feature.
- bpo-34658: Fix a rare interpreter unhandled exception state SystemError only seen when using subprocess with a preexec_fn while an after_parent handler has been registered with os.register_at_fork and the fork system call fails.
- bpo-34652: Ensure `os.lchmod()` is never defined on Linux.
- bpo-34363: dataclasses.asdict() and .astuple() now handle namedtuples correctly.
- bpo-34625: Update vendorized expat library version to 2.2.6.
- bpo-34621: Fix un/pickling compatbility of uuid.UUID objects with older versions of Python (<3.7).
- bpo-32270: The subprocess module no longer mistakenly closes redirected fds even when they were in pass_fds when outside of the default {0, 1, 2} set.
- bpo-34610: Fixed iterator of `multiprocessing.managers.DictProxy`.
- bpo-34421: Fix distutils logging for non-ASCII strings. This caused installation issues on Windows.
- bpo-34604: Fix possible mojibake in the error message of `pwd.getpwnam` and `grp.getgrnam`. Patch by William Grzybowski.
- bpo-34530: `distutils.spawn.find_executable()` now falls back on `os.defpath` if the `PATH` environment variable is not set.
- bpo-34282: Fix enum members getting shadowed by parent attributes.
- bpo-34563: On Windows, fix multiprocessing.Connection for very large read: fix _winapi.PeekNamedPipe() and _winapi.ReadFile() for read larger than INT_MAX (usually 2^31-1).
- bpo-34558: Correct typo in Lib/ctypes/_aix.py
- bpo-34515: Fix parsing non-ASCII identifiers in `lib2to3.pgen2.tokenize` (PEP 3131).
- bpo-13312: Avoids a possible integer underflow (undefined behavior) in the time module’s year handling code when passed a very low negative year value.
- bpo-34472: Improved compatibility for streamed files in `zipfile`. Previously an optional signature was not being written and certain ZIP applications were not supported. Patch by Silas Sewell.
- bpo-34454: Fix the .fromisoformat() methods of datetime types crashing when given unicode with non-UTF-8-encodable code points. Specifically, datetime.fromisoformat() now accepts surrogate unicode code points used as the separator. Report and tests by Alexey Izbyshev, patch by Paul Ganssle.
- bpo-6700: Fix inspect.getsourcelines for module level frames/tracebacks. Patch by Vladimir Matveev.
- bpo-34171: Running the `trace` module no longer creates the `trace.cover` file.
- bpo-34441: Fix crash when an `ABC`-derived class with invalid `__subclasses__` is passed as the second argument to `issubclass()`. Patch by Alexey Izbyshev.
- bpo-34341: Appending to the ZIP archive with the ZIP64 extension no longer grows the size of extra fields of existing entries.
- bpo-34333: Fix %-formatting in `pathlib.PurePath.with_suffix()` when formatting an error message.
- bpo-18540: The `imaplib.IMAP4` and `imaplib.IMAP4_SSL` classes now resolve to the local host IP correctly when the default value of host parameter (`''`) is used.
- bpo-34246: `smtplib.SMTP.send_message()` no longer modifies the content of the mail_options argument. Patch by Pablo S. Blum de Aguiar.
- bpo-31047: Fix `ntpath.abspath` for invalid paths on windows. Patch by Franz Woellert.
- bpo-34263: asyncio’s event loop will not pass timeouts longer than one day to epoll/select etc.
- bpo-34035: Fix several AttributeError in zipfile seek() methods. Patch by Mickaël Schoentgen.
- bpo-32215: Fix performance regression in `sqlite3` when a DML statement appeared in a different line than the rest of the SQL query.
- bpo-34251: Restore `msilib.Win64` to preserve backwards compatibility since it’s already used by `distutils`’ `bdist_msi` command.
- bpo-19891: Ignore errors caused by missing / non-writable homedir while writing history during exit of an interactive session. Patch by Anthony Sottile.
- bpo-34213: Allow frozen dataclasses to have a field named “object”. Previously this conflicted with an internal use of “object”.
- bpo-21446: The `reload` fixer now uses `importlib.reload()` instead of deprecated `imp.reload()`.
- bpo-940286: pydoc’s `Helper.showtopic()` method now prints the cross references of a topic correctly.
- bpo-34164: `base64.b32decode()` could raise UnboundLocalError or OverflowError for incorrect padding. Now it always raises `base64.Error` in these cases.
- bpo-33729: Fixed issues with arguments parsing in `hashlib`.
- bpo-34108: Remove extraneous CR in 2to3 refactor.
- bpo-27494: Reverted bpo-27494. 2to3 rejects now a trailing comma in generator expressions.
- bpo-33967: functools.singledispatch now raises TypeError instead of IndexError when no positional arguments are passed.
- bpo-34056: Ensure the loader shim created by `imp.load_module` always returns bytes from its `get_data()` function. This fixes using `imp.load_module` with PEP 552 hash-based pycs.
- bpo-34054: The multiprocessing module now uses the monotonic clock `time.monotonic()` instead of the system clock `time.time()` to implement timeout.
- bpo-34044: `subprocess.Popen` now copies the startupinfo argument to leave it unchanged: it will modify the copy, so that the same `STARTUPINFO` object can be used multiple times.
- bpo-34010: Fixed a performance regression for reading streams with tarfile. The buffered read should use a list, instead of appending to a bytes object.
- bpo-34019: webbrowser: Correct the arguments passed to Opera Browser when opening a new URL using the `webbrowser` module. Patch by Bumsik Kim.
- bpo-33978: Closed existing logging handlers before reconfiguration via fileConfig and dictConfig. Patch by Karthikeyan Singaravelan.
- bpo-14117: Make minor tweaks to turtledemo. The ‘wikipedia’ example is now ‘rosette’, decribing what it draws. The ‘penrose’ print output is reduced. The‘1024’ output of ‘tree’ is eliminated.
- bpo-33974: Fixed passing lists and tuples of strings containing special characters `"`, `\`, `{`, `}` and `\n` as options to `ttk` widgets.
- bpo-27500: Fix getaddrinfo to resolve IPv6 addresses correctly.
- bpo-24567: Improve random.choices() to handle subnormal input weights that could occasionally trigger an IndexError.
- bpo-33871: Fixed integer overflow in `os.readv()`, `os.writev()`, `os.preadv()` and `os.pwritev()` and in `os.sendfile()` with headers or trailers arguments (on BSD-based OSes and macOS).
- bpo-33899: Tokenize module now implicitly emits a NEWLINE when provided with input that does not have a trailing new line. This behavior now matches what the C tokenizer does internally. Contributed by Ammar Askar.
- bpo-33916: bz2 and lzma: When Decompressor.__init__() is called twice, free the old lock to not leak memory.
- bpo-32568: Make select.epoll() and its documentation consistent regarding sizehint and flags.
- bpo-33833: Fixed bug in asyncio where ProactorSocketTransport logs AssertionError if force closed during write.
- bpo-33663: Convert content length to string before putting to header.
- bpo-26544: Fixed implementation of `platform.libc_ver()`. It almost always returned version ‘2.9’ for glibc.
- bpo-33805: Improve error message of dataclasses.replace() when an InitVar is not specified
- bpo-27397: Make email module properly handle invalid-length base64 strings.
- bpo-33476: Fix _header_value_parser.py when address group is missing final ‘;’. Contributed by Enrique Perez-Terron
- bpo-31014: Fixed creating a controller for `webbrowser` when a user specifies a path to an entry in the BROWSER environment variable. Based on patch by John Still.
- bpo-33365: Print the header values besides the header keys instead just the header keys if debuglevel is set to >0 in `http.client`. Patch by Marco Strigl.
- bpo-32933: `unittest.mock.mock_open()` now supports iteration over the file contents. Patch by Tony Flury.
- bpo-33336: `imaplib` now allows `MOVE` command in `IMAP4.uid()` (RFC 6851: IMAP MOVE Extension) and potentially as a name of supported method of `IMAP4` object.
- bpo-31608: Raise a `TypeError` instead of crashing if a `collections.deque` subclass returns a non-deque from `__new__`. Patch by Oren Milman.
- bpo-29456: Fix bugs in hangul normalization: u1176, u11a7 and u11c3

### Documentation

- bpo-34790: Document how passing coroutines to asyncio.wait() can be confusing.
- bpo-28617: Fixed info in the stdtypes docs concerning the types that support membership tests.
- bpo-34065: Fix wrongly written basicConfig documentation markup syntax
- bpo-33460: replaced ellipsis with correct error codes in tutorial chapter 3.
- bpo-33847: Add ‘@’ operator entry to index.
- bpo-25041: Document `AF_PACKET` in the `socket` module.

### Tests

- bpo-34537: Fix `test_gdb.test_strings()` when `LC_ALL=C` and GDB was compiled with Python 3.6 or earlier.
- bpo-34587: test_socket: Remove RDSTest.testCongestion(). The test tries to fill the receiver’s socket buffer and expects an error. But the RDS protocol doesn’t require that. Moreover, the Linux implementation of RDS expects that the producer of the messages reduces its rate, it’s not the role of the receiver to trigger an error. The test fails on Fedora 28 by design, so just remove it.
- bpo-34661: Fix test_shutil if unzip doesn’t support -t.
- bpo-34200: Fixed non-deterministic flakiness of test_pkg by not using the scary test.support.module_cleanup() logic to save and restore sys.modules contents between test cases.
- bpo-34594: Fix usage of hardcoded `errno` values in the tests.
- bpo-34542: Use 3072 RSA keys and SHA-256 signature for test certs and keys.
- bpo-11193: Remove special condition for AIX in `test_subprocess.test_undecodable_env`
- bpo-34490: On AIX with AF_UNIX family sockets getsockname() does not provide ‘sockname’, so skip calls to transport.get_extra_info(‘sockname’)
- bpo-34391: Fix ftplib test for TLS 1.3 by reading from data socket.
- bpo-34399: Update all RSA keys and DH params to use at least 2048 bits.
- bpo-33746: Fix test_unittest when run in verbose mode.
- bpo-33901: Fix test_dbm_gnu on macOS with gdbm 1.15: add a larger value to make sure that the file size changes.
- bpo-33873: Fix a bug in `regrtest` that caused an extra test to run if –huntrleaks/-R was used. Exit with error in case that invalid parameters are specified to –huntrleaks/-R (at least one warmup run and one repetition must be used).
- bpo-32663: Making sure the `SMTPUTF8SimTests` class of tests gets run in test_smtplib.py.

### Build

- bpo-34710: Fixed SSL module build with OpenSSL & pedantic CFLAGS.
- bpo-34582: Add JUnit XML output for regression tests and update Azure DevOps builds.
- bpo-34555: Fix for case where it was not possible to have both `HAVE_LINUX_VM_SOCKETS_H` and `HAVE_SOCKADDR_ALG` be undefined.
- bpo-34121: Fix detection of C11 atomic support on clang.
- bpo-30345: Add -g to LDFLAGS when compiling with LTO to get debug symbols.
- bpo-33648: The –with-c-locale-warning configuration flag has been removed. It has had no effect for about a year.

### Windows

- bpo-34770: Fix a possible null pointer dereference in pyshellext.cpp.
- bpo-34603: Fix returning structs from functions produced by MSVC
- bpo-34581: Guard MSVC-specific code in socketmodule.c with `#ifdef _MSC_VER`.
- bpo-34062: Fixed the ‘–list’ and ‘–list-paths’ arguments for the py.exe launcher
- bpo-34225: Ensure INCLUDE and LIB directories do not end with a backslash.
- bpo-34006: Revert line length limit for Windows help docs. The line-length limit is not needed because the pages appear in a separate app rather than on a browser tab. It can also interact badly with the DPI setting.
- bpo-31546: Restore running PyOS_InputHook while waiting for user input at the prompt. The restores integration of interactive GUI windows (such as Matplotlib figures) with the prompt on Windows.
- bpo-30237: Output error when ReadConsole is canceled by CancelSynchronousIo instead of crashing.
- bpo-29097: Fix bug where `datetime.fromtimestamp()` erronously throws an `OSError` on Windows for values between 0 and 86400. Patch by Ammar Askar.

### macOS

- bpo-34370: Have macOS 10.9+ installer builds for 3.7.1rc and 3.6.7rc use a development snapshot of Tk 8.6 (post-8.6.8) to mitigate certain scroller issues seen with IDLE and tkinter apps.
- bpo-34405: Update to OpenSSL 1.1.0i for macOS installer builds.
- bpo-33635: In macOS stat on some file descriptors (/dev/fd/3 f.e) will result in bad file descriptor OSError. Guard against this exception was added in is_dir, is_file and similar methods. DirEntry.is_dir can also throw this exception so _RecursiveWildcardSelector._iterate_directories was also extended with the same error ignoring pattern.
- bpo-31903: In `_scproxy`, drop the GIL when calling into `SystemConfiguration` to avoid deadlocks.

### IDLE

- bpo-34548: Use configured color theme for read-only text views.
- bpo-1529353: Enable “squeezing” of long outputs in the shell, to avoid performance degradation and to clean up the history without losing it. Squeezed outputs may be copied, viewed in a separate window, and “unsqueezed”.
- bpo-34047: Fixed mousewheel scrolling direction on macOS.
- bpo-34275: Make IDLE calltips always visible on Mac. Some MacOS-tk combinations need .update_idletasks(). Patch by Kevin Walzer.
- bpo-34120: Fix unresponsiveness after closing certain windows and dialogs.
- bpo-33975: Avoid small type when running htests. Since part of the purpose of human-viewed tests is to determine that widgets look right, it is important that they look the same for testing as when running IDLE.
- bpo-33905: Add test for idlelib.stackview.StackBrowser.
- bpo-33924: Change mainmenu.menudefs key ‘windows’ to ‘window’. Every other menudef key is lowercase version of main menu entry.
- bpo-33906: Rename idlelib.windows as window Match Window on the main menu and remove last plural module name.
- bpo-33917: Fix and document idlelib/idle_test/template.py. The revised file compiles, runs, and tests OK. idle_test/README.txt explains how to use it to create new IDLE test files.
- bpo-33904: IDLE: In rstrip, rename class RstripExtension as Rstrip
- bpo-33907: For consistency and clarity, rename an IDLE module and classes. Module calltips and its class CallTips are now calltip and Calltip. In module calltip_w, class CallTip is now CalltipWindow.
- bpo-33856: Add “help” in the welcome message of IDLE
- bpo-33839: IDLE: refactor ToolTip and CallTip and add documentation and tests
- bpo-33855: Minimally test all IDLE modules. Add missing files, import module, instantiate classes, and check coverage. Check existing files.

### Tools/Demos

- bpo-32962: python-gdb now catchs `UnicodeDecodeError` exceptions when calling `string()`.
- bpo-32962: python-gdb now catchs ValueError on read_var(): when Python has no debug symbols for example.

### C API

- bpo-34247: Fix Py_Initialize() regression introduced in 3.7.0: read environment variables like PYTHONOPTIMIZE.
- bpo-23927: Fixed `SystemError` in `PyArg_ParseTupleAndKeywords()` when the `w*` format unit is used for optional parameter.
- bpo-34008: Py_Main() can again be called after Py_Initialize(), as in Python 3.6.

## Python 3.7.0 final

Release date: 2018-06-27

### Library

- bpo-33851: Fix `ast.get_docstring()` for a node that lacks a docstring.

### C API

- bpo-33932: Calling Py_Initialize() twice does nothing, instead of failing with a fatal error: restore the Python 3.6 behaviour.

## Python 3.7.0 release candidate 1

Release date: 2018-06-12

### Core and Builtins

- bpo-33803: Fix a crash in hamt.c caused by enabling GC tracking for an object that hadn’t all of its fields set to NULL.
- bpo-33706: Fix a crash in Python initialization when parsing the command line options. Thanks Christoph Gohlke for the bug report and the fix!
- bpo-30654: Fixed reset of the SIGINT handler to SIG_DFL on interpreter shutdown even when there was a custom handler set previously. Patch by Philipp Kerling.
- bpo-31849: Fix signed/unsigned comparison warning in pyhash.c.

### Library

- bpo-30167: Prevent site.main() exception if PYTHONSTARTUP is set. Patch by Steve Weber.
- bpo-33812: Datetime instance d with non-None tzinfo, but with d.tzinfo.utcoffset(d) returning None is now treated as naive by the astimezone() method.
- bpo-30805: Avoid race condition with debug logging
- bpo-33694: asyncio: Fix a race condition causing data loss on pause_reading()/resume_reading() when using the ProactorEventLoop.
- bpo-32493: Correct test for `uuid_enc_be` availability in `configure.ac`. Patch by Michael Felt.
- bpo-33792: Add asyncio.WindowsSelectorEventLoopPolicy and asyncio.WindowsProactorEventLoopPolicy.
- bpo-33778: Update `unicodedata`’s database to Unicode version 11.0.0.
- bpo-33770: improve base64 exception message for encoded inputs of invalid length
- bpo-33769: asyncio/start_tls: Fix error message; cancel callbacks in case of an unhandled error; mark SSLTransport as closed if it is aborted.
- bpo-33767: The concatenation (`+`) and repetition (`*`) sequence operations now raise `TypeError` instead of `SystemError` when performed on `mmap.mmap` objects. Patch by Zackery Spytz.
- bpo-33734: asyncio/ssl: Fix AttributeError, increase default handshake timeout
- bpo-11874: Use a better regex when breaking usage into wrappable parts. Avoids bogus assertion errors from custom metavar strings.
- bpo-33582: Emit a deprecation warning for inspect.formatargspec

### Documentation

- bpo-33409: Clarified the relationship between PEP 538’s PYTHONCOERCECLOCALE and PEP 540’s PYTHONUTF8 mode.
- bpo-33736: Improve the documentation of `asyncio.open_connection()`, `asyncio.start_server()` and their UNIX socket counterparts.
- bpo-31432: Clarify meaning of CERT_NONE, CERT_OPTIONAL, and CERT_REQUIRED flags for ssl.SSLContext.verify_mode.

### Build

- bpo-5755: Move `-Wstrict-prototypes` option to `CFLAGS_NODIST` from `OPT`. This option emitted annoying warnings when building extension modules written in C++.

### Windows

- bpo-33720: Reduces maximum marshal recursion depth on release builds.

### IDLE

- bpo-33656: On Windows, add API call saying that tk scales for DPI. On Windows 8.1+ or 10, with DPI compatibility properties of the Python binary unchanged, and a monitor resolution greater than 96 DPI, this should make text and lines sharper. It should otherwise have no effect.
- bpo-33768: Clicking on a context line moves that line to the top of the editor window.
- bpo-33763: IDLE: Use read-only text widget for code context instead of label widget.
- bpo-33664: Scroll IDLE editor text by lines. Previously, the mouse wheel and scrollbar slider moved text by a fixed number of pixels, resulting in partial lines at the top of the editor box. The change also applies to the shell and grep output windows, but not to read-only text views.
- bpo-33679: Enable theme-specific color configuration for Code Context. Use the Highlights tab to see the setting for built-in themes or add settings to custom themes.
- bpo-33642: Display up to maxlines non-blank lines for Code Context. If there is no current context, show a single blank line.

## Python 3.7.0 beta 5

Release date: 2018-05-30

### Core and Builtins

- bpo-33622: Fixed a leak when the garbage collector fails to add an object with the `__del__` method or referenced by it into the `gc.garbage` list. `PyGC_Collect()` can now be called when an exception is set and preserves it.
- bpo-33509: Fix module_globals parameter of warnings.warn_explicit(): don’t crash if module_globals is not a dict.
- bpo-20104: The new `os.posix_spawn` added in 3.7.0b1 was removed as we are still working on what the API should look like. Expect this in 3.8 instead.
- bpo-33475: Fixed miscellaneous bugs in converting annotations to strings and optimized parentheses in the string representation.
- bpo-33391: Fix a leak in set_symmetric_difference().
- bpo-28055: Fix unaligned accesses in siphash24(). Patch by Rolf Eike Beer.
- bpo-32911: Due to unexpected compatibility issues discovered during downstream beta testing, reverted bpo-29463. `docstring` field is removed from Module, ClassDef, FunctionDef, and AsyncFunctionDef ast nodes which was added in 3.7a1. Docstring expression is restored as a first statement in their body. Based on patch by Inada Naoki.
- bpo-21983: Fix a crash in `ctypes.cast()` in case the type argument is a ctypes structured data type. Patch by Eryk Sun and Oren Milman.

### Library

- bpo-32751: When cancelling the task due to a timeout, `asyncio.wait_for()` will now wait until the cancellation is complete.
- bpo-32684: Fix gather to propagate cancellation of itself even with return_exceptions.
- bpo-33654: Support protocol type switching in SSLTransport.set_protocol().
- bpo-33674: Pause the transport as early as possible to further reduce the risk of data_received() being called before connection_made().
- bpo-33674: Fix a race condition in SSLProtocol.connection_made() of asyncio.sslproto: start immediately the handshake instead of using call_soon(). Previously, data_received() could be called before the handshake started, causing the handshake to hang or fail.
- bpo-31647: Fixed bug where calling write_eof() on a _SelectorSocketTransport after it’s already closed raises AttributeError.
- bpo-32610: Make asyncio.all_tasks() return only pending tasks.
- bpo-32410: Avoid blocking on file IO in sendfile fallback code
- bpo-33469: Fix RuntimeError after closing loop that used run_in_executor
- bpo-33672: Fix Task.__repr__ crash with Cython’s bogus coroutines
- bpo-33654: Fix transport.set_protocol() to support switching between asyncio.Protocol and asyncio.BufferedProtocol. Fix loop.start_tls() to work with asyncio.BufferedProtocols.
- bpo-33652: Pickles of type variables and subscripted generics are now future-proof and compatible with older Python versions.
- bpo-32493: Fixed `uuid.uuid1()` on FreeBSD.
- bpo-33618: Finalize and document preliminary and experimental TLS 1.3 support with OpenSSL 1.1.1
- bpo-33623: Fix possible SIGSGV when asyncio.Future is created in __del__
- bpo-30877: Fixed a bug in the Python implementation of the JSON decoder that prevented the cache of parsed strings from clearing after finishing the decoding. Based on patch by c-fos.
- bpo-33570: Change TLS 1.3 cipher suite settings for compatibility with OpenSSL 1.1.1-pre6 and newer. OpenSSL 1.1.1 will have TLS 1.3 ciphers enabled by default.
- bpo-28556: Do not simplify arguments to `typing.Union`. Now `Union[Manager, Employee]` is not simplified to `Employee` at runtime. Such simplification previously caused several bugs and limited possibilities for introspection.
- bpo-33540: Add a new `block_on_close` class attribute to `ForkingMixIn` and `ThreadingMixIn` classes of `socketserver`.
- bpo-33548: tempfile._candidate_tempdir_list should consider common TEMP locations
- bpo-33109: argparse subparsers are once again not required by default, reverting the change in behavior introduced by bpo-26510 in 3.7.0a2.
- bpo-33536: dataclasses.make_dataclass now checks for invalid field names and duplicate fields. Also, added a check for invalid field specifications.
- bpo-33542: Prevent `uuid.get_node` from using a DUID instead of a MAC on Windows. Patch by Zvi Effron
- bpo-26819: Fix race condition with `ReadTransport.resume_reading` in Windows proactor event loop.
- Fix failure in `typing.get_type_hints()` when ClassVar was provided as a string forward reference.
- bpo-33505: Optimize asyncio.ensure_future() by reordering if checks: 1.17x faster.
- bpo-33497: Add errors param to cgi.parse_multipart and make an encoding in FieldStorage use the given errors (needed for Twisted). Patch by Amber Brown.
- bpo-33495: Change dataclasses.Fields repr to use the repr of each of its members, instead of str. This makes it more clear what each field actually represents. This is especially true for the ‘type’ member.
- bpo-33453: Fix dataclasses to work if using literal string type annotations or if using PEP 563 “Postponed Evaluation of Annotations”. Only specific string prefixes are detected for both ClassVar (“ClassVar” and “typing.ClassVar”) and InitVar (“InitVar” and “dataclasses.InitVar”).
- bpo-28556: Minor fixes in typing module: add annotations to `NamedTuple.__new__`, pass `*args` and `**kwds` in `Generic.__new__`. Original PRs by Paulius Šarka and Chad Dombrova.
- bpo-20087: Updated alias mapping with glibc 2.27 supported locales.
- bpo-33422: Fix trailing quotation marks getting deleted when looking up byte/string literals on pydoc. Patch by Andrés Delfino.
- bpo-28167: The function `platform.linux_distribution` and `platform.dist` now trigger a `DeprecationWarning` and have been marked for removal in Python 3.8
- bpo-33197: Update error message when constructing invalid inspect.Parameters Patch by Dong-hee Na.
- bpo-33263: Fix FD leak in `_SelectorSocketTransport` Patch by Vlad Starostin.
- bpo-32861: The urllib.robotparser’s `__str__` representation now includes wildcard entries and the “Crawl-delay” and “Request-rate” fields. Patch by Michael Lazar.
- bpo-32257: The ssl module now contains OP_NO_RENEGOTIATION constant, available with OpenSSL 1.1.0h or 1.1.1.
- bpo-16865: Support arrays >=2GiB in `ctypes`. Patch by Segev Finer.

### Documentation

- bpo-23859: Document that `asyncio.wait()` does not cancel its futures on timeout.
- bpo-32436: Document PEP 567 changes to asyncio.
- bpo-33604: Update HMAC md5 default to a DeprecationWarning, bump removal to 3.8.
- bpo-33503: Fix broken pypi link
- bpo-33421: Add missing documentation for `typing.AsyncContextManager`.

### Tests

- bpo-33655: Ignore test_posix_fallocate failures on BSD platforms that might be due to running on ZFS.
- bpo-32604: Remove the _xxsubinterpreters module (meant for testing) and associated helpers. This module was originally added recently in 3.7b1.

### Build

- bpo-33614: Ensures module definition files for the stable ABI on Windows are correctly regenerated.
- bpo-33522: Enable CI builds on Visual Studio Team Services at https://python.visualstudio.com/cpython
- bpo-33012: Add `-Wno-cast-function-type` for gcc 8 for silencing warnings about function casts like casting to PyCFunction in method definition lists.

### macOS

- bpo-13631: The .editrc file in user’s home directory is now processed correctly during the readline initialization through editline emulation on macOS.

### IDLE

- bpo-33628: IDLE: Cleanup codecontext.py and its test.
- bpo-33564: IDLE’s code context now recognizes async as a block opener.
- bpo-32831: Add docstrings and tests for codecontext.

## Python 3.7.0 beta 4

Release date: 2018-05-02

### Core and Builtins

- bpo-33363: Raise a SyntaxError for `async with` and `async for` statements outside of async functions.
- bpo-33128: Fix a bug that causes PathFinder to appear twice on sys.meta_path. Patch by Pablo Galindo Salgado.
- bpo-33312: Fixed clang ubsan (undefined behavior sanitizer) warnings in dictobject.c by adjusting how the internal struct _dictkeysobject shared keys structure is declared.
- bpo-33231: Fix potential memory leak in `normalizestring()`.
- bpo-33205: Change dict growth function from `round_up_to_power_2(used*2+hashtable_size/2)` to `round_up_to_power_2(used*3)`. Previously, dict is shrinked only when `used == 0`. Now dict has more chance to be shrinked.
- bpo-29922: Improved error messages in ‘async with’ when `__aenter__()` or `__aexit__()` return non-awaitable object.
- bpo-33199: Fix `ma_version_tag` in dict implementation is uninitialized when copying from key-sharing dict.

### Library

- bpo-33281: Fix ctypes.util.find_library regression on macOS.

- bpo-33383: Fixed crash in the get() method of the `dbm.ndbm` database object when it is called with a single argument.

- bpo-33329: Fix multiprocessing regression on newer glibcs

- bpo-991266: Fix quoting of the `Comment` attribute of `http.cookies.SimpleCookie`.

- bpo-33131: Upgrade bundled version of pip to 10.0.1.

- bpo-33308: Fixed a crash in the `parser` module when converting an ST object to a tree of tuples or lists with `line_info=False` and `col_info=True`.

- bpo-33266: lib2to3 now recognizes `rf'...'` strings.

- bpo-11594: Ensure line-endings are respected when using lib2to3.

- bpo-33254: Have `importlib.resources.contents()` and `importlib.abc.ResourceReader.contents()` return an iterable instead of an iterator.

- bpo-33256: Fix display of `<module>` call in the html produced by `cgitb.html()`. Patch by Stéphane Blondon.

- bpo-33185: Fixed regression when running pydoc with the `-m` switch. (The regression was introduced in 3.7.0b3 by the resolution of bpo-33053)

  This fix also changed pydoc to add `os.getcwd()` to `sys.path` when necessary, rather than adding `"."`.

- bpo-33169: Delete entries of `None` in `sys.path_importer_cache` when `importlib.machinery.invalidate_caches()` is called.

- bpo-33217: Deprecate looking up non-Enum objects in Enum classes and Enum members (will raise `TypeError` in 3.8+).

- bpo-33203: `random.Random.choice()` now raises `IndexError` for empty sequences consistently even when called from subclasses without a `getrandbits()` implementation.

- bpo-33224: Update difflib.mdiff() for PEP 479. Convert an uncaught StopIteration in a generator into a return-statement.

- bpo-33209: End framing at the end of C implementation of `pickle.Pickler.dump()`.

- bpo-20104: Improved error handling and fixed a reference leak in `os.posix_spawn()`.

- bpo-33175: In dataclasses, Field.__set_name__ now looks up the __set_name__ special method on the class, not the instance, of the default value.

- bpo-33097: Raise RuntimeError when `executor.submit` is called during interpreter shutdown.

- bpo-31908: Fix output of cover files for `trace` module command-line tool. Previously emitted cover files only when `--missing` option was used. Patch by Michael Selik.

### Documentation

- bpo-33378: Add Korean language switcher for https://docs.python.org/3/
- bpo-33276: Clarify that the `__path__` attribute on modules cannot be just any value.
- bpo-33201: Modernize documentation for writing C extension types.
- bpo-33195: Deprecate `Py_UNICODE` usage in `c-api/arg` document. `Py_UNICODE` related APIs are deprecated since Python 3.3, but it is missed in the document.
- bpo-8243: Add a note about curses.addch and curses.addstr exception behavior when writing outside a window, or pad.
- bpo-32337: Update documentation related with `dict` order.

### Tests

- bpo-33358: Fix `test_embed.test_pre_initialization_sys_options()` when the interpreter is built with `--enable-shared`.

### Build

- bpo-33394: Enable the verbose build for extension modules, when GNU make is passed macros on the command line.
- bpo-33393: Update config.guess and config.sub files.
- bpo-33377: Add new triplets for mips r6 and riscv variants (used in extension suffixes).
- bpo-32232: By default, modules configured in `Modules/Setup` are no longer built with `-DPy_BUILD_CORE`. Instead, modules that specifically need that preprocessor definition include it in their individual entries.
- bpo-33182: The embedding tests can once again be built with clang 6.0

### Windows

- bpo-33184: Update Windows installer to use OpenSSL 1.1.0h.

### macOS

- bpo-33184: Update macOS installer build to use OpenSSL 1.1.0h.

### IDLE

- bpo-21474: Update word/identifier definition from ascii to unicode. In text and entry boxes, this affects selection by double-click, movement left/right by control-left/right, and deletion left/right by control-BACKSPACE/DEL.
- bpo-33204: IDLE: consistently color invalid string prefixes. A ‘u’ string prefix cannot be paired with either ‘r’ or ‘f’. Consistently color as much of the prefix, starting at the right, as is valid. Revise and extend colorizer test.

### Tools/Demos

- bpo-33189: pygettext.py now recognizes only literal strings as docstrings and translatable strings, and rejects bytes literals and f-string expressions.
- bpo-31920: Fixed handling directories as arguments in the `pygettext` script. Based on patch by Oleg Krasnikov.
- bpo-29673: Fix pystackv and pystack gdbinit macros.
- bpo-31583: Fix 2to3 for using with –add-suffix option but without –output-dir option for relative path to files in current directory.

## Python 3.7.0 beta 3

Release date: 2018-03-29

### Security

- bpo-33136: Harden ssl module against LibreSSL CVE-2018-8970. X509_VERIFY_PARAM_set1_host() is called with an explicit namelen. A new test ensures that NULL bytes are not allowed.
- bpo-33001: Minimal fix to prevent buffer overrun in os.symlink on Windows
- bpo-32981: Regexes in difflib and poplib were vulnerable to catastrophic backtracking. These regexes formed potential DOS vectors (REDOS). They have been refactored. This resolves CVE-2018-1060 and CVE-2018-1061. Patch by Jamie Davis.

### Core and Builtins

- bpo-33053: When using the -m switch, sys.path[0] is now explicitly expanded as the starting working directory, rather than being left as the empty path (which allows imports from the current working directory at the time of the import)
- bpo-33018: Improve consistency of errors raised by `issubclass()` when called with a non-class and an abstract base class as the first and second arguments, respectively. Patch by Josh Bronson.
- bpo-33041: Fixed jumping when the function contains an `async for` loop.
- bpo-33026: Fixed jumping out of “with” block by setting f_lineno.
- bpo-33005: Fix a crash on fork when using a custom memory allocator (ex: using PYTHONMALLOC env var). _PyGILState_Reinit() and _PyInterpreterState_Enable() now use the default RAW memory allocator to allocate a new interpreters mutex on fork.
- bpo-17288: Prevent jumps from ‘return’ and ‘exception’ trace events.
- bpo-32836: Don’t use temporary variables in cases of list/dict/set comprehensions

### Library

- bpo-33141: Have Field objects pass through __set_name__ to their default values, if they have their own __set_name__.
- bpo-33096: Allow ttk.Treeview.insert to insert iid that has a false boolean value. Note iid=0 and iid=False would be same. Patch by Garvit Khatri.
- bpo-32873: Treat type variables and special typing forms as immutable by copy and pickle. This fixes several minor issues and inconsistencies, and improves backwards compatibility with Python 3.6.
- bpo-33134: When computing dataclass’s __hash__, use the lookup table to contain the function which returns the __hash__ value. This is an improvement over looking up a string, and then testing that string to see what to do.
- bpo-33127: The ssl module now compiles with LibreSSL 2.7.1.
- bpo-32505: Raise TypeError if a member variable of a dataclass is of type Field, but doesn’t have a type annotation.
- bpo-33078: Fix the failure on OSX caused by the tests relying on sem_getvalue
- bpo-33116: Add ‘Field’ to dataclasses.__all__.
- bpo-32896: Fix an error where subclassing a dataclass with a field that uses a default_factory would generate an incorrect class.
- bpo-33100: Dataclasses: If a field has a default value that’s a MemberDescriptorType, then it’s from that field being in __slots__, not an actual default value.
- bpo-32953: If a non-dataclass inherits from a frozen dataclass, allow attributes to be added to the derived class. Only attributes from the frozen dataclass cannot be assigned to. Require all dataclasses in a hierarchy to be either all frozen or all non-frozen.
- bpo-33061: Add missing `NoReturn` to `__all__` in typing.py
- bpo-33078: Fix the size handling in multiprocessing.Queue when a pickling error occurs.
- bpo-33064: lib2to3 now properly supports trailing commas after `*args` and `**kwargs` in function signatures.
- bpo-33056: FIX properly close leaking fds in concurrent.futures.ProcessPoolExecutor.
- bpo-33021: Release the GIL during fstat() calls, avoiding hang of all threads when calling mmap.mmap(), os.urandom(), and random.seed(). Patch by Nir Soffer.
- bpo-31804: Avoid failing in multiprocessing.Process if the standard streams are closed or None at exit.
- bpo-33037: Skip sending/receiving data after SSL transport closing.
- bpo-27683: Fix a regression in `ipaddress` that result of `hosts()` is empty when the network is constructed by a tuple containing an integer mask and only 1 bit left for addresses.
- bpo-32999: Fix C implementation of `ABC.__subclasscheck__(cls, subclass)` crashed when `subclass` is not a type object.
- bpo-33009: Fix inspect.signature() for single-parameter partialmethods.
- bpo-32969: Expose several missing constants in zlib and fix corresponding documentation.
- bpo-32056: Improved exceptions raised for invalid number of channels and sample width when read an audio file in modules `aifc`, `wave` and `sunau`.
- bpo-32844: Fix wrong redirection of a low descriptor (0 or 1) to stderr in subprocess if another low descriptor is closed.
- bpo-32857: In `tkinter`, `after_cancel(None)` now raises a `ValueError` instead of canceling the first scheduled function. Patch by Cheryl Sabella.
- bpo-31639: http.server now exposes a ThreadedHTTPServer class and uses it when the module is run with `-m` to cope with web browsers pre-opening sockets.
- bpo-27645: `sqlite3.Connection` now exposes a `backup` method, if the underlying SQLite library is at version 3.6.11 or higher. Patch by Lele Gaifax.

### Documentation

- bpo-33126: Document PyBuffer_ToContiguous().
- bpo-27212: Modify documentation for the `islice()` recipe to consume initial values up to the start index.
- bpo-28247: Update `zipapp` documentation to describe how to make standalone applications.
- bpo-18802: Documentation changes for ipaddress. Patch by Jon Foster and Berker Peksag.
- bpo-27428: Update documentation to clarify that `WindowsRegistryFinder` implements `MetaPathFinder`. (Patch by Himanshu Lakhara)

### Tests

- bpo-32872: Avoid regrtest compatibility issue with namespace packages.
- bpo-32517: Fix failing `test_asyncio` on macOS 10.12.2+ due to transport of `KqueueSelector` loop was not being closed.
- bpo-19417: Add test_bdb.py.

### Build

- bpo-33163: Upgrade pip to 9.0.3 and setuptools to v39.0.1.

### Windows

- bpo-33016: Fix potential use of uninitialized memory in nt._getfinalpathname
- bpo-32903: Fix a memory leak in os.chdir() on Windows if the current directory is set to a UNC path.

### macOS

- bpo-32726: Build and link with private copy of Tcl/Tk 8.6 for the macOS 10.6+ installer. The 10.9+ installer variant already does this. This means that the Python 3.7 provided by the python.org macOS installers no longer need or use any external versions of Tcl/Tk, either system-provided or user-installed, such as ActiveTcl.

### IDLE

- bpo-32984: Set `__file__` while running a startup file. Like Python, IDLE optionally runs one startup file in the Shell window before presenting the first interactive input prompt. For IDLE, `-s` runs a file named in environmental variable `IDLESTARTUP` or `PYTHONSTARTUP`; `-r file` runs `file`. Python sets `__file__` to the startup file name before running the file and unsets it before the first prompt. IDLE now does the same when run normally, without the `-n` option.
- bpo-32940: Simplify and rename StringTranslatePseudoMapping in pyparse.

### Tools/Demos

- bpo-32885: Add an `-n` flag for `Tools/scripts/pathfix.py` to disable automatic backup creation (files with `~` suffix).

### C API

- bpo-33042: Embedding applications may once again call PySys_ResetWarnOptions, PySys_AddWarnOption, and PySys_AddXOption prior to calling Py_Initialize.
- bpo-32374: Document that m_traverse for multi-phase initialized modules can be called with m_state=NULL, and add a sanity check

## Python 3.7.0 beta 2

Release date: 2018-02-27

### Security

- bpo-28414: The ssl module now allows users to perform their own IDN en/decoding when using SNI.

### Core and Builtins

- bpo-32889: Update Valgrind suppression list to account for the rename of `Py_ADDRESS_IN_RANG` to `address_in_range`.
- bpo-31356: Remove the new API added in bpo-31356 (gc.ensure_disabled() context manager).
- bpo-32305: For namespace packages, ensure that both `__file__` and `__spec__.origin` are set to None.
- bpo-32303: Make sure `__spec__.loader` matches `__loader__` for namespace packages.
- bpo-32711: Fix the warning messages for Python/ast_unparse.c. Patch by Stéphane Wirtel
- bpo-32583: Fix possible crashing in builtin Unicode decoders caused by write out-of-bound errors when using customized decode error handlers.

### Library

- bpo-32960: For dataclasses, disallow inheriting frozen from non-frozen classes, and also disallow inheriting non-frozen from frozen classes. This restriction will be relaxed at a future date.

- bpo-32713: Fixed tarfile.itn handling of out-of-bounds float values. Patch by Joffrey Fuhrer.

- bpo-32951: Direct instantiation of SSLSocket and SSLObject objects is now prohibited. The constructors were never documented, tested, or designed as public constructors. Users were suppose to use ssl.wrap_socket() or SSLContext.

- bpo-32929: Remove the tri-state parameter “hash”, and add the boolean “unsafe_hash”. If unsafe_hash is True, add a __hash__ function, but if a __hash__ exists, raise TypeError. If unsafe_hash is False, add a __hash__ based on the values of eq= and frozen=. The unsafe_hash=False behavior is the same as the old hash=None behavior. unsafe_hash=False is the default, just as hash=None used to be.

- bpo-32947: Add OP_ENABLE_MIDDLEBOX_COMPAT and test workaround for TLSv1.3 for future compatibility with OpenSSL 1.1.1.

- bpo-30622: The ssl module now detects missing NPN support in LibreSSL.

- bpo-32922: dbm.open() now encodes filename with the filesystem encoding rather than default encoding.

- bpo-32859: In `os.dup2`, don’t check every call whether the `dup3` syscall exists or not.

- bpo-32556: nt._getfinalpathname, nt._getvolumepathname and nt._getdiskusage now correctly convert from bytes.

- bpo-25988: Emit a `DeprecationWarning` when using or importing an ABC directly from `collections` rather than from `collections.abc`.

- bpo-21060: Rewrite confusing message from setup.py upload from “No dist file created in earlier command” to the more helpful “Must create and upload files in one command”.

- bpo-32852: Make sure sys.argv remains as a list when running trace.

- bpo-31333: `_abc` module is added. It is a speedup module with C implementations for various functions and methods in `abc`. Creating an ABC subclass and calling `isinstance` or `issubclass` with an ABC subclass are up to 1.5x faster. In addition, this makes Python start-up up to 10% faster.

  Note that the new implementation hides internal registry and caches, previously accessible via private attributes `_abc_registry`, `_abc_cache`, and `_abc_negative_cache`. There are three debugging helper methods that can be used instead `_dump_registry`, `_abc_registry_clear`, and `_abc_caches_clear`.

- bpo-32841: Fixed `asyncio.Condition` issue which silently ignored cancellation after notifying and cancelling a conditional lock. Patch by Bar Harel.

- bpo-32819: ssl.match_hostname() has been simplified and no longer depends on re and ipaddress module for wildcard and IP addresses. Error reporting for invalid wildcards has been improved.

- bpo-32394: socket: Remove TCP_FASTOPEN,TCP_KEEPCNT,TCP_KEEPIDLE,TCP_KEEPINTVL flags on older version Windows during run-time.

- bpo-31787: Fixed refleaks of `__init__()` methods in various modules. (Contributed by Oren Milman)

- bpo-30157: Fixed guessing quote and delimiter in csv.Sniffer.sniff() when only the last field is quoted. Patch by Jake Davis.

- bpo-32792: collections.ChainMap() preserves the order of the underlying mappings.

- bpo-32775: `fnmatch.translate()` no longer produces patterns which contain set operations. Sets starting with ‘[‘ or containing ‘–’, ‘&&’, ‘~~’ or ‘||’ will be interpreted differently in regular expressions in future versions. Currently they emit warnings. fnmatch.translate() now avoids producing patterns containing such sets by accident.

- bpo-32622: Implement native fast sendfile for Windows proactor event loop.

- bpo-32777: Fix a rare but potential pre-exec child process deadlock in subprocess on POSIX systems when marking file descriptors inheritable on exec in the child process. This bug appears to have been introduced in 3.4.

- bpo-32647: The ctypes module used to depend on indirect linking for dlopen. The shared extension is now explicitly linked against libdl on platforms with dl.

- bpo-32741: Implement `asyncio.TimerHandle.when()` method.

- bpo-32691: Use mod_spec.parent when running modules with pdb

- bpo-32734: Fixed `asyncio.Lock()` safety issue which allowed acquiring and locking the same lock multiple times, without it being free. Patch by Bar Harel.

- bpo-32727: Do not include name field in SMTP envelope from address. Patch by Stéphane Wirtel

- bpo-31453: Add TLSVersion constants and SSLContext.maximum_version / minimum_version attributes. The new API wraps OpenSSL 1.1 https://www.openssl.org/docs/man1.1.0/ssl/SSL_CTX_set_min_proto_version.html feature.

- bpo-24334: Internal implementation details of ssl module were cleaned up. The SSLSocket has one less layer of indirection. Owner and session information are now handled by the SSLSocket and SSLObject constructor. Channel binding implementation has been simplified.

- bpo-31848: Fix the error handling in Aifc_read.initfp() when the SSND chunk is not found. Patch by Zackery Spytz.

- bpo-32585: Add Ttk spinbox widget to `tkinter.ttk`. Patch by Alan D Moore.

- bpo-32221: Various functions returning tuple containing IPv6 addresses now omit `%scope` part since the same information is already encoded in scopeid tuple item. Especially this speeds up `socket.recvfrom()` when it receives multicast packet since useless resolving of network interface name is omitted.

- bpo-30693: The TarFile class now recurses directories in a reproducible way.

- bpo-30693: The ZipFile class now recurses directories in a reproducible way.

### Documentation

- bpo-28124: The ssl module function ssl.wrap_socket() has been de-emphasized and deprecated in favor of the more secure and efficient SSLContext.wrap_socket() method.
- bpo-17232: Clarify docs for -O and -OO. Patch by Terry Reedy.
- bpo-32436: Add documentation for the contextvars module (PEP 567).
- bpo-32800: Update link to w3c doc for xml default namespaces.
- bpo-11015: Update `test.support` documentation.
- bpo-8722: Document `__getattr__()` behavior when property `get()` method raises `AttributeError`.
- bpo-32614: Modify RE examples in documentation to use raw strings to prevent `DeprecationWarning` and add text to REGEX HOWTO to highlight the deprecation.
- bpo-31972: Improve docstrings for `pathlib.PurePath` subclasses.

### Tests

- bpo-31809: Add tests to verify connection with secp ECDH curves.

### Build

- bpo-32898: Fix the python debug build when using COUNT_ALLOCS.

### Windows

- bpo-32901: Update Tcl and Tk versions to 8.6.8
- bpo-31966: Fixed WindowsConsoleIO.write() for writing empty data.
- bpo-32409: Ensures activate.bat can handle Unicode contents.
- bpo-32457: Improves handling of denormalized executable path when launching Python.
- bpo-32370: Use the correct encoding for ipconfig output in the uuid module. Patch by Segev Finer.
- bpo-29248: Fix `os.readlink()` on Windows, which was mistakenly treating the `PrintNameOffset` field of the reparse data buffer as a number of characters instead of bytes. Patch by Craig Holmquist and SSE4.

### macOS

- bpo-32901: Update macOS 10.9+ installer to Tcl/Tk 8.6.8.

### IDLE

- bpo-32916: Change `str` to `code` in pyparse.
- bpo-32905: Remove unused code in pyparse module.
- bpo-32874: Add tests for pyparse.
- bpo-32837: Using the system and place-dependent default encoding for open() is a bad idea for IDLE’s system and location-independent files.
- bpo-32826: Add “encoding=utf-8” to open() in IDLE’s test_help_about. GUI test test_file_buttons() only looks at initial ascii-only lines, but failed on systems where open() defaults to ‘ascii’ because readline() internally reads and decodes far enough ahead to encounter a non-ascii character in CREDITS.txt.
- bpo-32765: Update configdialog General tab docstring to add new widgets to the widget list.

### Tools/Demos

- bpo-32222: Fix pygettext not extracting docstrings for functions with type annotated arguments. Patch by Toby Harradine.

## Python 3.7.0 beta 1

Release date: 2018-01-30

### Core and Builtins

- bpo-32703: Fix coroutine’s ResourceWarning when there’s an active error set when it’s being finalized.

- bpo-32650: Pdb and other debuggers dependent on bdb.py will correctly step over (next command) native coroutines. Patch by Pablo Galindo.

- bpo-28685: Optimize list.sort() and sorted() by using type specialized comparisons when possible.

- bpo-32685: Improve suggestion when the Python 2 form of print statement is either present on the same line as the header of a compound statement or else terminated by a semi-colon instead of a newline. Patch by Nitish Chandra.

- bpo-32697: Python now explicitly preserves the definition order of keyword-only parameters. It’s always preserved their order, but this behavior was never guaranteed before; this behavior is now guaranteed and tested.

- bpo-32690: The locals() dictionary now displays in the lexical order that variables were defined. Previously, the order was reversed.

- bpo-32677: Add `.isascii()` method to `str`, `bytes` and `bytearray`. It can be used to test that string contains only ASCII characters.

- bpo-32670: Enforce PEP 479 for all code.

  This means that manually raising a StopIteration exception from a generator is prohibited for all code, regardless of whether ‘from __future__ import generator_stop’ was used or not.

- bpo-32591: Added built-in support for tracking the origin of coroutine objects; see sys.set_coroutine_origin_tracking_depth and CoroutineType.cr_origin. This replaces the asyncio debug mode’s use of coroutine wrapping for native coroutine objects.

- bpo-31368: Expose preadv and pwritev system calls in the os module. Patch by Pablo Galindo

- bpo-32544: `hasattr(obj, name)` and `getattr(obj, name, default)` are about 4 times faster than before when `name` is not found and `obj` doesn’t override `__getattr__` or `__getattribute__`.

- bpo-26163: Improved frozenset() hash to create more distinct hash values when faced with datasets containing many similar values.

- bpo-32550: Remove the STORE_ANNOTATION bytecode.

- bpo-20104: Expose posix_spawn as a low level API in the os module. (removed before 3.7.0rc1)

- bpo-24340: Fixed estimation of the code stack size.

- bpo-32436: Implement PEP 567 Context Variables.

- bpo-18533: `repr()` on a dict containing its own `values()` or `items()` no longer raises `RecursionError`; OrderedDict similarly. Instead, use `...`, as for other recursive structures. Patch by Ben North.

- bpo-20891: Py_Initialize() now creates the GIL. The GIL is no longer created “on demand” to fix a race condition when PyGILState_Ensure() is called in a non-Python thread.

- bpo-32028: Leading whitespace is now correctly ignored when generating suggestions for converting Py2 print statements to Py3 builtin print function calls. Patch by Sanyam Khurana.

- bpo-31179: Make dict.copy() up to 5.5 times faster.

- bpo-31113: Get rid of recursion in the compiler for normal control flow.

### Library

- bpo-25988: Deprecate exposing the contents of collections.abc in the regular collections module.

- bpo-31429: The default cipher suite selection of the ssl module now uses a blacklist approach rather than a hard-coded whitelist. Python no longer re-enables ciphers that have been blocked by OpenSSL security update. Default cipher suite selection can be configured on compile time.

- bpo-30306: contextlib.contextmanager now releases the arguments passed to the underlying generator as soon as the context manager is entered. Previously it would keep them alive for as long as the context manager was alive, even when not being used as a function decorator. Patch by Martin Teichmann.

- bpo-21417: Added support for setting the compression level for zipfile.ZipFile.

- bpo-32251: Implement asyncio.BufferedProtocol (provisional API).

- bpo-32513: In dataclasses, allow easier overriding of dunder methods without specifying decorator parameters.

- bpo-32660: `termios` makes available `FIONREAD`, `FIONCLEX`, `FIOCLEX`, `FIOASYNC` and `FIONBIO` also under Solaris/derivatives.

- bpo-27931: Fix email address header parsing error when the username is an empty quoted string. Patch by Xiang Zhang.

- bpo-32659: Under Solaris and derivatives, `os.stat_result` provides a st_fstype attribute.

- bpo-32662: Implement Server.start_serving(), Server.serve_forever(), and Server.is_serving() methods. Add ‘start_serving’ keyword parameter to loop.create_server() and loop.create_unix_server().

- bpo-32391: Implement `asyncio.StreamWriter.wait_closed()` and `asyncio.StreamWriter.is_closing()` methods

- bpo-32643: Make Task._step, Task._wakeup and Future._schedule_callbacks methods private.

- bpo-32630: Refactor decimal module to use contextvars to store decimal context.

- bpo-32622: Add `asyncio.AbstractEventLoop.sendfile()` method.

- bpo-32304: distutils’ upload command no longer corrupts tar files ending with a CR byte, and no longer tries to convert CR to CRLF in any of the upload text fields.

- bpo-32502: uuid.uuid1 no longer raises an exception if a 64-bit hardware address is encountered.

- bpo-32596: `concurrent.futures` imports `ThreadPoolExecutor` and `ProcessPoolExecutor` lazily (using PEP 562). It makes `import asyncio` about 15% faster because asyncio uses only `ThreadPoolExecutor` by default.

- bpo-31801: Add `_ignore_` to `Enum` so temporary variables can be used during class construction without being turned into members.

- bpo-32576: Use queue.SimpleQueue() in places where it can be invoked from a weakref callback.

- bpo-32574: Fix memory leak in asyncio.Queue, when the queue has limited size and it is full, the cancelation of queue.put() can cause a memory leak. Patch by: José Melero.

- bpo-32521: The nis module is now compatible with new libnsl and headers location.

- bpo-32467: collections.abc.ValuesView now inherits from collections.abc.Collection.

- bpo-32473: Improve ABCMeta._dump_registry() output readability

- bpo-32102: New argument `capture_output` for subprocess.run

- bpo-32521: glibc has removed Sun RPC. Use replacement libtirpc headers and library in nis module.

- bpo-32493: UUID module fixes build for FreeBSD/OpenBSD

- bpo-32503: Pickling with protocol 4 no longer creates too small frames.

- bpo-29237: Create enum for pstats sorting options

- bpo-32454: Add close(fd) function to the socket module.

- bpo-25942: The subprocess module is now more graceful when handling a Ctrl-C KeyboardInterrupt during subprocess.call, subprocess.run, or a Popen context manager. It now waits a short amount of time for the child (presumed to have also gotten the SIGINT) to exit, before continuing the KeyboardInterrupt exception handling. This still includes a SIGKILL in the call() and run() APIs, but at least the child had a chance first.

- bpo-32433: The hmac module now has hmac.digest(), which provides an optimized HMAC digest.

- bpo-28134: Sockets now auto-detect family, type and protocol from file descriptor by default.

- bpo-32404: Fix bug where `datetime.datetime.fromtimestamp()` did not call __new__ in `datetime.datetime` subclasses.

- bpo-32403: Improved speed of `datetime.date` and `datetime.datetime` alternate constructors.

- bpo-32228: Ensure that `truncate()` preserves the file position (as reported by `tell()`) after writes longer than the buffer size.

- bpo-32410: Implement `loop.sock_sendfile` for asyncio event loop.

- bpo-22908: Added seek and tell to the ZipExtFile class. This only works if the file object used to open the zipfile is seekable.

- bpo-32373: Add socket.getblocking() method.

- bpo-32248: Add `importlib.resources` and `importlib.abc.ResourceReader` as the unified API for reading resources contained within packages. Loaders wishing to support resource reading must implement the `get_resource_reader()` method. File-based and zipimport-based loaders both implement these APIs. `importlib.abc.ResourceLoader` is deprecated in favor of these new APIs.

- bpo-32320: collections.namedtuple() now supports default values.

- bpo-29302: Add contextlib.AsyncExitStack. Patch by Alexander Mohr and Ilya Kulakov.

- bpo-31961: Removed in Python 3.7.0b2. The args argument of subprocess.Popen can now be a path-like object. If args is given as a sequence, it’s first element can now be a path-like object as well.

- bpo-31900: The `locale.localeconv()` function now sets temporarily the `LC_CTYPE` locale to the `LC_NUMERIC` locale to decode `decimal_point` and `thousands_sep` byte strings if they are non-ASCII or longer than 1 byte, and the `LC_NUMERIC` locale is different than the `LC_CTYPE` locale. This temporary change affects other threads.

  Same change for the `str.format()` method when formatting a number (`int`, `float`, `float` and subclasses) with the `n` type (ex: `'{:n}'.format(1234)`).

- bpo-31853: Use super().method instead of socket.method in SSLSocket. They were there most likely for legacy reasons.

- bpo-31399: The ssl module now uses OpenSSL’s X509_VERIFY_PARAM_set1_host() and X509_VERIFY_PARAM_set1_ip() API to verify hostname and IP addresses. Subject common name fallback can be disabled with SSLContext.hostname_checks_common_name.

- bpo-14976: Add a queue.SimpleQueue class, an unbounded FIFO queue with a reentrant C implementation of put().

### Documentation

- bpo-32724: Add references to some commands in the documentation of Pdb. Patch by Stéphane Wirtel
- bpo-32649: Complete the C API documentation, profiling and tracing part with the newly added per-opcode events.
- bpo-17799: Explain real behaviour of sys.settrace and sys.setprofile and their C-API counterparts regarding which type of events are received in each function. Patch by Pablo Galindo Salgado.

### Tests

- bpo-32721: Fix test_hashlib to not fail if the _md5 module is not built.

- bpo-28414: Add test cases for IDNA 2003 and 2008 host names. IDNA 2003 internationalized host names are working since bpo-31399 has landed. IDNA 2008 are still broken.

- bpo-32604: Add a new “_xxsubinterpreters” extension module that exposes the existing subinterpreter C-API and a new cross-interpreter data sharing mechanism. The module is primarily intended for more thorough testing of the existing subinterpreter support.

  Note that the _xxsubinterpreters module has been removed in 3.7.0rc1.

- bpo-32602: Add test certs and test for ECDSA cert and EC/RSA dual mode.

- bpo-32549: On Travis CI, Python now Compiles and uses a local copy of OpenSSL 1.1.0g for testing.

### Build

- bpo-32635: Fix segfault of the crypt module when libxcrypt is provided instead of libcrypt at the system.
- bpo-32598: Use autoconf to detect OpenSSL libs, headers and supported features. The ax_check_openssl M4 macro uses pkg-config to locate OpenSSL and falls back to manual search.
- bpo-32593: Drop support of FreeBSD 9 and older.
- bpo-29708: If the `SOURCE_DATE_EPOCH` environment variable is set, `py_compile` will always create hash-based `.pyc` files.

### Windows

- bpo-32588: Create standalone _distutils_findvs module and add missing _queue module to installer.
- bpo-29911: Ensure separate Modify and Uninstall buttons are displayed.
- bpo-32507: Use app-local UCRT install rather than the proper update for old versions of Windows.

### macOS

- bpo-32726: Provide an additional, more modern macOS installer variant that supports macOS 10.9+ systems in 64-bit mode only. Upgrade the supplied third-party libraries to OpenSSL 1.1.0g and to SQLite 3.22.0. The 10.9+ installer now links with and supplies its own copy of Tcl/Tk 8.6.
- bpo-28440: No longer add /Library/Python/3.x/site-packages to sys.path for macOS framework builds to avoid future conflicts.

### C API

- bpo-32681: Fix uninitialized variable ‘res’ in the C implementation of os.dup2. Patch by Stéphane Wirtel
- bpo-10381: Add C API access to the `datetime.timezone` constructor and `datetime.timzone.UTC` singleton.

## Python 3.7.0 alpha 4

Release date: 2018-01-08

### Core and Builtins

- bpo-31975: The default warning filter list now starts with a “default::DeprecationWarning:__main__” entry, so deprecation warnings are once again shown by default in single-file scripts and at the interactive prompt.
- bpo-32226: `__class_getitem__` is now an automatic class method.
- bpo-32399: Add AIX uuid library support for RFC4122 using uuid_create() in libc.a
- bpo-32390: Fix the compilation failure on AIX after the f_fsid field has been added to the object returned by os.statvfs() (bpo-32143). Original patch by Michael Felt.
- bpo-32379: Make MRO computation faster when a class inherits from a single base.
- bpo-32259: The error message of a TypeError raised when unpack non-iterable is now more specific.
- bpo-27169: The `__debug__` constant is now optimized out at compile time. This fixes also bpo-22091.
- bpo-32329: The `-R` option now turns on hash randomization when the `PYTHONHASHSEED` environment variable is set to `0`. Previously, the option was ignored. Moreover, `sys.flags.hash_randomization` is now properly set to 0 when hash randomization is turned off by `PYTHONHASHSEED=0`.
- bpo-30416: The optimizer is now protected from spending much time doing complex calculations and consuming much memory for creating large constants in constant folding. Increased limits for constants that can be produced in constant folding.
- bpo-32282: Fix an unnecessary ifdef in the include of VersionHelpers.h in socketmodule on Windows.
- bpo-30579: Implement TracebackType.__new__ to allow Python-level creation of traceback objects, and make TracebackType.tb_next mutable.
- bpo-32260: Don’t byte swap the input keys to the SipHash algorithm on big-endian platforms. This should ensure siphash gives consistent results across platforms.
- bpo-31506: Improve the error message logic for object.__new__ and object.__init__. Patch by Sanyam Khurana.
- bpo-20361: `-b` and `-bb` now inject `'default::BytesWarning'` and `error::BytesWarning` entries into `sys.warnoptions`, ensuring that they take precedence over any other warning filters configured via the `-W` option or the `PYTHONWARNINGS` environment variable.
- bpo-32230: `-X dev` now injects a `'default'` entry into sys.warnoptions, ensuring that it behaves identically to actually passing `-Wdefault` at the command line.
- bpo-29240: Add a new UTF-8 mode: implementation of the PEP 540.
- bpo-32226: PEP 560: Add support for `__mro_entries__` and `__class_getitem__`. Implemented by Ivan Levkivskyi.
- bpo-32225: PEP 562: Add support for module `__getattr__` and `__dir__`. Implemented by Ivan Levkivskyi.
- bpo-31901: The `atexit` module now has its callback stored per interpreter.
- bpo-31650: Implement PEP 552 (Deterministic pycs). Python now supports invalidating bytecode cache files bashed on a source content hash rather than source last-modified time.
- bpo-29469: Move constant folding from bytecode layer to AST layer. Original patch by Eugene Toder.

### Library

- bpo-32506: Now that dict is defined as keeping insertion order, drop OrderedDict and just use plain dict.

- bpo-32279: Add params to dataclasses.make_dataclasses(): init, repr, eq, order, hash, and frozen. Pass them through to dataclass().

- bpo-32278: Make type information optional on dataclasses.make_dataclass(). If omitted, the string ‘typing.Any’ is used.

- bpo-32499: Add dataclasses.is_dataclass(obj), which returns True if obj is a dataclass or an instance of one.

- bpo-32468: Improve frame repr() to mention filename, code name and current line number.

- bpo-23749: asyncio: Implement loop.start_tls()

- bpo-32441: Return the new file descriptor (i.e., the second argument) from `os.dup2`. Previously, `None` was always returned.

- bpo-32422: `functools.lru_cache` uses less memory (3 words for each cached key) and takes about 1/3 time for cyclic GC.

- bpo-31721: Prevent Python crash from happening when Future._log_traceback is set to True manually. Now it can only be set to False, or a ValueError is raised.

- bpo-32415: asyncio: Add Task.get_loop() and Future.get_loop()

- bpo-26133: Don’t unsubscribe signals in asyncio UNIX event loop on interpreter shutdown.

- bpo-32363: Make asyncio.Task.set_exception() and set_result() raise NotImplementedError. Task._step() and Future.__await__() raise proper exceptions when they are in an invalid state, instead of raising an AssertionError.

- bpo-32357: Optimize asyncio.iscoroutine() and loop.create_task() for non-native coroutines (e.g. async/await compiled with Cython).

  ‘loop.create_task(python_coroutine)’ used to be 20% faster than ‘loop.create_task(cython_coroutine)’. Now, the latter is as fast.

- bpo-32356: asyncio.transport.resume_reading() and pause_reading() are now idempotent. New transport.is_reading() method is added.

- bpo-32355: Optimize asyncio.gather(); now up to 15% faster.

- bpo-32351: Use fastpath in asyncio.sleep if delay<0 (2x boost)

- bpo-32348: Optimize asyncio.Future schedule/add/remove callback. The optimization shows 3-6% performance improvements of async/await code.

- bpo-32331: Fix socket.settimeout() and socket.setblocking() to keep socket.type as is. Fix socket.socket() constructor to reset any bit flags applied to socket’s type. This change only affects OSes that have SOCK_NONBLOCK and/or SOCK_CLOEXEC.

- bpo-32248: Add `importlib.abc.ResourceReader` as an ABC for loaders to provide a unified API for reading resources contained within packages. Also add `importlib.resources` as the port of `importlib_resources`.

- bpo-32311: Implement asyncio.create_task(coro) shortcut

- bpo-32327: Convert asyncio functions that were documented as coroutines to coroutines. Affected functions: loop.sock_sendall, loop.sock_recv, loop.sock_accept, loop.getaddrinfo, loop.getnameinfo.

- bpo-32323: `urllib.parse.urlsplit()` does not convert zone-id (scope) to lower case for scoped IPv6 addresses in hostnames now.

- bpo-32302: Fix bdist_wininst of distutils for CRT v142: it binary compatible with CRT v140.

- bpo-29711: Fix `stop_serving` in asyncio proactor loop kill all listening servers

- bpo-32308: `re.sub()` now replaces empty matches adjacent to a previous non-empty match.

- bpo-29970: Abort asyncio SSLProtocol connection if handshake not complete within 10s

- bpo-32314: Implement asyncio.run().

- bpo-17852: Revert incorrect fix based on misunderstanding of _Py_PyAtExit() semantics.

- bpo-32296: Implement asyncio._get_running_loop() and get_event_loop() in C. This makes them 4x faster.

- bpo-32250: Implement `asyncio.current_task()` and `asyncio.all_tasks()`. Add helpers intended to be used by alternative task implementations: `asyncio._register_task`, `asyncio._enter_task`, `asyncio._leave_task` and `asyncio._unregister_task`. Deprecate `asyncio.Task.current_task()` and `asyncio.Task.all_tasks()`.

- bpo-32255: A single empty field is now always quoted when written into a CSV file. This allows to distinguish an empty row from a row consisting of a single empty field. Patch by Licht Takeuchi.

- bpo-32277: Raise `NotImplementedError` instead of `SystemError` on platforms where `chmod(..., follow_symlinks=False)` is not supported. Patch by Anthony Sottile.

- bpo-30050: New argument warn_on_full_buffer to signal.set_wakeup_fd lets you control whether Python prints a warning on stderr when the wakeup fd buffer overflows.

- bpo-29137: The `fpectl` library has been removed. It was never enabled by default, never worked correctly on x86-64, and it changed the Python ABI in ways that caused unexpected breakage of C extensions.

- bpo-32273: Move asyncio.test_utils to test.test_asyncio.

- bpo-32272: Remove asyncio.async() function.

- bpo-32269: Add asyncio.get_running_loop() function.

- bpo-32265: All class and static methods of builtin types now are correctly classified by inspect.classify_class_attrs() and grouped in pydoc ouput. Added types.ClassMethodDescriptorType for unbound class methods of builtin types.

- bpo-32253: Deprecate `yield from lock`, `await lock`, `with (yield from lock)` and `with await lock` for asyncio synchronization primitives.

- bpo-22589: Changed MIME type of .bmp from ‘image/x-ms-bmp’ to ‘image/bmp’

- bpo-32193: Convert asyncio to use async/await syntax. Old styled `yield from` is still supported too.

- bpo-32206: Add support to run modules with pdb

- bpo-32227: `functools.singledispatch` now supports registering implementations using type annotations.

- bpo-15873: Added new alternate constructors `datetime.datetime.fromisoformat()`, `datetime.time.fromisoformat()` and `datetime.date.fromisoformat()` as the inverse operation of each classes’s respective `isoformat` methods.

- bpo-32199: The getnode() ip getter now uses ‘ip link’ instead of ‘ip link list’.

- bpo-32143: os.statvfs() includes the f_fsid field from statvfs(2)

- bpo-26439: Fix ctypes.util.find_library() for AIX by implementing ctypes._aix.find_library() Patch by: Michael Felt

- bpo-31993: The pickler now uses less memory when serializing large bytes and str objects into a file. Pickles created with protocol 4 will require less memory for unpickling large bytes and str objects.

- bpo-27456: Ensure TCP_NODELAY is set on Linux. Tests by Victor Stinner.

- bpo-31778: ast.literal_eval() is now more strict. Addition and subtraction of arbitrary numbers no longer allowed.

- bpo-31802: Importing native path module (`posixpath`, `ntpath`) now works even if the `os` module still is not imported.

- bpo-30241: Add contextlib.AbstractAsyncContextManager. Patch by Jelle Zijlstra.

- bpo-31699: Fix deadlocks in `concurrent.futures.ProcessPoolExecutor` when task arguments or results cause pickling or unpickling errors. This should make sure that calls to the `ProcessPoolExecutor` API always eventually return.

- bpo-15216: `TextIOWrapper.reconfigure()` supports changing encoding, errors, and newline.

### Documentation

- bpo-32418: Add get_loop() method to Server and AbstractServer classes.

### Tests

- bpo-32252: Fix faulthandler_suppress_crash_report() used to prevent core dump files when testing crashes. getrlimit() returns zero on success.
- bpo-32002: Adjust C locale coercion testing for the empty locale and POSIX locale cases to more readily adjust to platform dependent behaviour.

### Windows

- bpo-19764: Implement support for `subprocess.Popen(close_fds=True)` on Windows. Patch by Segev Finer.

### Tools/Demos

- bpo-24960: 2to3 and lib2to3 can now read pickled grammar files using pkgutil.get_data() rather than probing the filesystem. This lets 2to3 and lib2to3 work when run from a zipfile.

### C API

- bpo-32030: Py_Initialize() doesn’t reset the memory allocators to default if the `PYTHONMALLOC` environment variable is not set.
- bpo-29084: Undocumented C API for OrderedDict has been excluded from the limited C API. It was added by mistake and actually never worked in the limited C API.
- bpo-32264: Moved the pygetopt.h header into internal/, since it has no public APIs.
- bpo-32241: `Py_SetProgramName()` and `Py_SetPythonHome()` now take the `const wchar *` arguments instead of `wchar *`.

## Python 3.7.0 alpha 3

Release date: 2017-12-05

### Core and Builtins

- bpo-32176: co_flags.CO_NOFREE is now always set correctly by the code object constructor based on freevars and cellvars, rather than needing to be set correctly by the caller. This ensures it will be cleared automatically when additional cell references are injected into a modified code object and function.
- bpo-10544: Yield expressions are now deprecated in comprehensions and generator expressions. They are still permitted in the definition of the outermost iterable, as that is evaluated directly in the enclosing scope.
- bpo-32137: The repr of deeply nested dict now raises a RecursionError instead of crashing due to a stack overflow.
- bpo-32096: Revert memory allocator changes in the C API: move structures back from _PyRuntime to Objects/obmalloc.c. The memory allocators are once again initialized statically, and so PyMem_RawMalloc() and Py_DecodeLocale() can be called before _PyRuntime_Initialize().
- bpo-32043: Add a new “developer mode”: new “-X dev” command line option to enable debug checks at runtime.
- bpo-32023: SyntaxError is now correctly raised when a generator expression without parenthesis is used instead of an inheritance list in a class definition. The duplication of the parentheses can be omitted only on calls.
- bpo-32012: SyntaxError is now correctly raised when a generator expression without parenthesis is passed as an argument, but followed by a trailing comma. A generator expression always needs to be directly inside a set of parentheses and cannot have a comma on either side.
- bpo-28180: A new internal `_Py_SetLocaleFromEnv(category)` helper function has been added in order to improve the consistency of behaviour across different `libc` implementations (e.g. Android doesn’t support setting the locale from the environment by default).
- bpo-31949: Fixed several issues in printing tracebacks (PyTraceBack_Print()).
  - Setting sys.tracebacklimit to 0 or less now suppresses printing tracebacks.
  - Setting sys.tracebacklimit to None now causes using the default limit.
  - Setting sys.tracebacklimit to an integer larger than LONG_MAX now means using the limit LONG_MAX rather than the default limit.
  - Fixed integer overflows in the case of more than 2**31 traceback items on Windows.
  - Fixed output errors handling.
- bpo-30696: Fix the interactive interpreter looping endlessly when no memory.
- bpo-20047: Bytearray methods partition() and rpartition() now accept only bytes-like objects as separator, as documented. In particular they now raise TypeError rather of returning a bogus result when an integer is passed as a separator.
- bpo-21720: BytesWarning no longer emitted when the fromlist argument of `__import__()` or the `__all__` attribute of the module contain bytes instances.
- bpo-31845: Environment variables are once more read correctly at interpreter startup.
- bpo-28936: Ensure that lexically first syntax error involving a parameter and `global` or `nonlocal` is detected first at a given scope. Patch by Ivan Levkivskyi.
- bpo-31825: Fixed OverflowError in the ‘unicode-escape’ codec and in codecs.escape_decode() when decode an escaped non-ascii byte.
- bpo-31618: The per-frame tracing logic added in 3.7a1 has been altered so that `frame->f_lineno` is updated before either `"line"` or `"opcode"` events are emitted. Previously, opcode events were emitted first, and therefore would occasionally see stale line numbers on the frame. The behavior of this feature has changed slightly as a result: when both `f_trace_lines` and `f_trace_opcodes` are enabled, line events now occur first.
- bpo-28603: Print the full context/cause chain of exceptions on interpreter exit, even if an exception in the chain is unhashable or compares equal to later ones. Patch by Zane Bitter.
- bpo-31786: Fix timeout rounding in the select module to round correctly negative timeouts between -1.0 and 0.0. The functions now block waiting for events as expected. Previously, the call was incorrectly non-blocking. Patch by Pablo Galindo.
- bpo-31781: Prevent crashes when calling methods of an uninitialized `zipimport.zipimporter` object. Patch by Oren Milman.
- bpo-30399: Standard repr() of BaseException with a single argument no longer contains redundant trailing comma.
- bpo-31626: Fixed a bug in debug memory allocator. There was a write to freed memory after shrinking a memory block.
- bpo-30817: `PyErr_PrintEx()` clears now the ignored exception that may be raised by `_PySys_SetObjectId()`, for example when no memory.

### Library

- bpo-28556: Two minor fixes for `typing` module: allow shallow copying instances of generic classes, improve interaction of `__init_subclass__` with generics. Original PRs by Ivan Levkivskyi.

- bpo-32214: PEP 557, Data Classes. Provides a decorator which adds boilerplate methods to classes which use type annotations so specify fields.

- bpo-27240: The header folding algorithm for the new email policies has been rewritten, which also fixes bpo-30788, bpo-31831, and bpo-32182. In particular, RFC2231 folding is now done correctly.

- bpo-32186: io.FileIO.readall() and io.FileIO.read() now release the GIL when getting the file size. Fixed hang of all threads with inaccessible NFS server. Patch by Nir Soffer.

- bpo-321010: Add `sys.flags.dev_mode` flag

- bpo-32154: The `asyncio.windows_utils.socketpair()` function has been removed: use directly `socket.socketpair()` which is available on all platforms since Python 3.5 (before, it wasn’t available on Windows). `asyncio.windows_utils.socketpair()` was just an alias to `socket.socketpair` on Python 3.5 and newer.

- bpo-32089: warnings: In development (-X dev) and debug mode (pydebug build), use the “default” action for ResourceWarning, rather than the “always” action, in the default warnings filters.

- bpo-32107: `uuid.getnode()` now preferentially returns universally administered MAC addresses if available, over locally administered MAC addresses. This makes a better guarantee for global uniqueness of UUIDs returned from `uuid.uuid1()`. If only locally administered MAC addresses are available, the first such one found is returned.

- bpo-23033: Wildcard is now supported in hostname when it is one and only character in the left most segment of hostname in second argument of `ssl.match_hostname()`. Patch by Mandeep Singh.

- bpo-12239: Make `msilib.SummaryInformation.GetProperty()` return `None` when the value of property is `VT_EMPTY`. Initial patch by Mark Mc Mahon.

- bpo-28334: Use `os.path.expanduser()` to find the `~/.netrc` file in `netrc.netrc`. If it does not exist, `FileNotFoundError` is raised. Patch by Dimitri Merejkowsky.

- bpo-32121: Made `tracemalloc.Traceback` behave more like the traceback module, sorting the frames from oldest to most recent. `Traceback.format()` now accepts negative limit, truncating the result to the `abs(limit)` oldest frames. To get the old behaviour, one can use the new most_recent_first argument to `Traceback.format()`. (Patch by Jesse Bakker.)

- bpo-31325: Fix wrong usage of `collections.namedtuple()` in the `RobotFileParser.parse()` method.

  Initial patch by Robin Wellner.

- bpo-12382: `msilib.OpenDatabase()` now raises a better exception message when it couldn’t open or create an MSI file. Initial patch by William Tisäter.

- bpo-19610: `setup()` now warns about invalid types for some fields.

  The `distutils.dist.Distribution` class now warns when `classifiers`, `keywords` and `platforms` fields are not specified as a list or a string.

- bpo-32071: Added the `-k` command-line option to `python -m unittest` to run only tests that match the given pattern(s).

- bpo-10049: Added nullcontext no-op context manager to contextlib. This provides a simpler and faster alternative to ExitStack() when handling optional context managers.

- bpo-28684: The new test.support.skip_unless_bind_unix_socket() decorator is used here to skip asyncio tests that fail because the platform lacks a functional bind() function for unix domain sockets (as it is the case for non root users on the recent Android versions that run now SELinux in enforcing mode).

- bpo-32110: `codecs.StreamReader.read(n)` now returns not more than n characters/bytes for non-negative n. This makes it compatible with `read()` methods of other file-like objects.

- bpo-27535: The warnings module doesn’t leak memory anymore in the hidden warnings registry for the “ignore” action of warnings filters. warn_explicit() function doesn’t add the warning key to the registry anymore for the “ignore” action.

- bpo-32088: warnings: When Python is build is debug mode (`Py_DEBUG`), `DeprecationWarning`, `PendingDeprecationWarning` and `ImportWarning` warnings are now displayed by default.

- bpo-1647489: Fixed searching regular expression patterns that could match an empty string. Non-empty string can now be correctly found after matching an empty string.

- bpo-25054: Added support of splitting on a pattern that could match an empty string.

- bpo-32072: Fixed issues with binary plists:

  - Fixed saving bytearrays.
  - Identical objects will be saved only once.
  - Equal references will be load as identical objects.
  - Added support for saving and loading recursive data structures.

- bpo-32069: Drop legacy SSL transport from asyncio, ssl.MemoryBIO is always used anyway.

- bpo-32066: asyncio: Support pathlib.Path in create_unix_connection; sock arg should be optional

- bpo-32046: Updates 2to3 to convert from operator.isCallable(obj) to callable(obj). Patch by Dong-hee Na.

- bpo-32018: inspect.signature should follow PEP 8, if the parameter has an annotation and a default value. Patch by Dong-hee Na.

- bpo-32025: Add time.thread_time() and time.thread_time_ns()

- bpo-32037: Integers that fit in a signed 32-bit integer will be now pickled with protocol 0 using the INT opcode. This will decrease the size of a pickle, speed up pickling and unpickling, and make these integers be unpickled as int instances in Python 2.

- bpo-32034: Make asyncio.IncompleteReadError and LimitOverrunError pickleable.

- bpo-32015: Fixed the looping of asyncio in the case of reconnection the socket during waiting async read/write from/to the socket.

- bpo-32011: Restored support of loading marshal files with the TYPE_INT64 code. These files can be produced in Python 2.7.

- bpo-28369: Enhance add_reader/writer check that socket is not used by some transport. Before, only cases when add_reader/writer were called with an int FD were supported. Now the check is implemented correctly for all file-like objects.

- bpo-31976: Fix race condition when flushing a file is slow, which can cause a segfault if closing the file from another thread.

- bpo-31985: Formally deprecated aifc.openfp, sunau.openfp, and wave.openfp. Since change 7bc817d5ba917528e8bd07ec461c635291e7b06a in 1993, openfp in each of the three modules had been pointing to that module’s open function as a matter of backwards compatibility, though it had been both untested and undocumented.

- bpo-21862: cProfile command line now accepts `-m module_name` as an alternative to script path. Patch by Sanyam Khurana.

- bpo-31970: Reduce performance overhead of asyncio debug mode.

- bpo-31843: database argument of sqlite3.connect() now accepts a path-like object, instead of just a string.

- bpo-31945: Add Configurable blocksize to `HTTPConnection` and `HTTPSConnection` for improved upload throughput. Patch by Nir Soffer.

- bpo-31943: Add a `cancelled()` method to `asyncio.Handle`. Patch by Marat Sharafutdinov.

- bpo-9678: Fixed determining the MAC address in the uuid module:

  - Using ifconfig on NetBSD and OpenBSD.
  - Using arp on Linux, FreeBSD, NetBSD and OpenBSD.

  Based on patch by Takayuki Shimizukawa.

- bpo-30057: Fix potential missed signal in signal.signal().

- bpo-31933: Fix Blake2 params leaf_size and node_offset on big endian platforms. Patch by Jack O’Connor.

- bpo-21423: Add an initializer argument to {Process,Thread}PoolExecutor

- bpo-31927: Fixed compilation of the socket module on NetBSD 8. Fixed assertion failure or reading arbitrary data when parse a AF_BLUETOOTH address on NetBSD and DragonFly BSD.

- bpo-27666: Fixed stack corruption in curses.box() and curses.ungetmouse() when the size of types chtype or mmask_t is less than the size of C long. curses.box() now accepts characters as arguments. Based on patch by Steve Fink.

- bpo-31917: Add 3 new clock identifiers: `time.CLOCK_BOOTTIME`, `time.CLOCK_PROF` and `time.CLOCK_UPTIME`.

- bpo-31897: plistlib now catches more errors when read binary plists and raises InvalidFileException instead of unexpected exceptions.

- bpo-25720: Fix the method for checking pad state of curses WINDOW. Patch by Masayuki Yamamoto.

- bpo-31893: Fixed the layout of the kqueue_event structure on OpenBSD and NetBSD. Fixed the comparison of the kqueue_event objects.

- bpo-31891: Fixed building the curses module on NetBSD.

- bpo-31884: added required constants to subprocess module for setting priority on windows

- bpo-28281: Remove year (1-9999) limits on the Calendar.weekday() function.

  Patch by Mark Gollahon.

- bpo-31702: crypt.mksalt() now allows to specify the number of rounds for SHA-256 and SHA-512 hashing.

- bpo-30639: `inspect.getfile()` no longer computes the repr of unknown objects to display in an error message, to protect against badly behaved custom reprs.

- bpo-30768: Fix the pthread+semaphore implementation of PyThread_acquire_lock_timed() when called with timeout > 0 and intr_flag=0: recompute the timeout if sem_timedwait() is interrupted by a signal (EINTR). See also the PEP 475.

- bpo-31854: Add `mmap.ACCESS_DEFAULT` constant.

- bpo-31834: Use optimized code for BLAKE2 only with SSSE3+. The pure SSE2 implementation is slower than the pure C reference implementation.

- bpo-28292: Calendar.itermonthdates() will now consistently raise an exception when a date falls outside of the 0001-01-01 through 9999-12-31 range. To support applications that cannot tolerate such exceptions, the new methods itermonthdays3() and itermonthdays4() are added. The new methods return tuples and are not restricted by the range supported by datetime.date.

- bpo-28564: The shutil.rmtree() function has been sped up to 20–40%. This was done using the os.scandir() function.

- bpo-28416: Instances of pickle.Pickler subclass with the persistent_id() method and pickle.Unpickler subclass with the persistent_load() method no longer create reference cycles.

- bpo-31653: Don’t release the GIL if we can acquire a multiprocessing semaphore immediately.

- bpo-28326: Fix multiprocessing.Process when stdout and/or stderr is closed or None.

- bpo-20825: Add `subnet_of` and `superset_of` containment tests to `ipaddress.IPv6Network` and `ipaddress.IPv4Network`. Patch by Michel Albert and Cheryl Sabella.

- bpo-31827: Remove the os.stat_float_times() function. It was introduced in Python 2.3 for backward compatibility with Python 2.2, and was deprecated since Python 3.1.

- bpo-31756: Add a `subprocess.Popen(text=False)` keyword argument to `subprocess` functions to be more explicit about when the library should attempt to decode outputs into text. Patch by Andrew Clegg.

- bpo-31819: Add AbstractEventLoop.sock_recv_into().

- bpo-31457: If nested log adapters are used, the inner `process()` methods are no longer omitted.

- bpo-31457: The `manager` property on LoggerAdapter objects is now properly settable.

- bpo-31806: Fix timeout rounding in time.sleep(), threading.Lock.acquire() and socket.socket.settimeout() to round correctly negative timeouts between -1.0 and 0.0. The functions now block waiting for events as expected. Previously, the call was incorrectly non-blocking. Patch by Pablo Galindo.

- bpo-31803: time.clock() and time.get_clock_info(‘clock’) now emit a DeprecationWarning warning.

- bpo-31800: Extended support for parsing UTC offsets. strptime ‘%z’ can now parse the output generated by datetime.isoformat, including seconds and microseconds.

- bpo-28603: traceback: Fix a TypeError that occurred during printing of exception tracebacks when either the current exception or an exception in its context/cause chain is unhashable. Patch by Zane Bitter.

- bpo-30541: Add new function to seal a mock and prevent the automatically creation of child mocks. Patch by Mario Corchero.

- bpo-31784: Implement the PEP 564, add new 6 new functions with nanosecond resolution to the `time` module: `clock_gettime_ns()`, `clock_settime_ns()`, `monotonic_ns()`, `perf_counter_ns()`, `process_time_ns()`, `time_ns()`.

- bpo-30143: 2to3 now generates a code that uses abstract collection classes from collections.abc rather than collections.

- bpo-31770: Prevent a crash when calling the `__init__()` method of a `sqlite3.Cursor` object more than once. Patch by Oren Milman.

- bpo-31764: Prevent a crash in `sqlite3.Cursor.close()` in case the `Cursor` object is uninitialized. Patch by Oren Milman.

- bpo-31752: Fix possible crash in timedelta constructor called with custom integers.

- bpo-31620: an empty asyncio.Queue now doesn’t leak memory when queue.get pollers timeout

- bpo-31690: Allow the flags re.ASCII, re.LOCALE, and re.UNICODE to be used as group flags for regular expressions.

- bpo-30349: FutureWarning is now emitted if a regular expression contains character set constructs that will change semantically in the future (nested sets and set operations).

- bpo-31664: Added support for the Blowfish hashing in the crypt module.

- bpo-31632: Fix method set_protocol() of class _SSLProtocolTransport in asyncio module. This method was previously modifying a wrong reference to the protocol.

- bpo-15037: Added a workaround for getkey() in curses for ncurses 5.7 and earlier.

- bpo-31307: Allow use of bytes objects for arguments to `configparser.ConfigParser.read()`. Patch by Vincent Michel.

- bpo-31334: Fix `poll.poll([timeout])` in the `select` module for arbitrary negative timeouts on all OSes where it can only be a non-negative integer or -1. Patch by Riccardo Coccioli.

- bpo-31310: multiprocessing’s semaphore tracker should be launched again if crashed.

- bpo-31308: Make multiprocessing’s forkserver process immune to Ctrl-C and other user interruptions. If it crashes, restart it when necessary.

- bpo-31245: Added support for AF_UNIX socket in asyncio `create_datagram_endpoint`.

- bpo-30553: Add HTTP/2 status code 421 (Misdirected Request) to `http.HTTPStatus`. Patch by Vitor Pereira.

### Documentation

- bpo-32105: Added asyncio.BaseEventLoop.connect_accepted_socket versionadded marker.

### Tests

- bpo-31380: Skip test_httpservers test_undecodable_file on macOS: fails on APFS.
- bpo-31705: Skip test_socket.test_sha256() on Linux kernel older than 4.5. The test fails with ENOKEY on kernel 3.10 (on ppc64le). A fix was merged into the kernel 4.5.
- bpo-32138: Skip on Android test_faulthandler tests that raise SIGSEGV and remove the test.support.requires_android_level decorator.
- bpo-32136: The runtime embedding tests have been split out from `Lib/test/test_capi.py` into a new `Lib/test/test_embed.py` file.
- bpo-28668: test.support.requires_multiprocessing_queue is removed. Skip tests with test.support.import_module(‘multiprocessing.synchronize’) instead when the semaphore implementation is broken or missing.
- bpo-32126: Skip test_get_event_loop_new_process in test.test_asyncio.test_events when sem_open() is not functional.
- bpo-31174: Fix test_tools.test_unparse: DirectoryTestCase now stores the names sample to always test the same files. It prevents false alarms when hunting reference leaks.

### Build

- bpo-28538: Revert the previous changes, the if_nameindex structure is defined by Unified Headers.
- bpo-28762: Revert the last commit, the F_LOCK macro is defined by Android Unified Headers.
- bpo-29040: Support building Android with Unified Headers. The first NDK release to support Unified Headers is android-ndk-r14.
- bpo-32059: `detect_modules()` in `setup.py` now also searches the sysroot paths when cross-compiling.
- bpo-31957: Fixes Windows SDK version detection when building for Windows.
- bpo-31609: Fixes quotes in PCbuild/clean.bat
- bpo-31934: Abort the build when building out of a not clean source tree.
- bpo-31926: Fixed Argument Clinic sometimes causing compilation errors when there was more than one function and/or method in a .c file with the same name.
- bpo-28791: Update Windows builds to use SQLite 3.21.0.
- bpo-28791: Update OS X installer to use SQLite 3.21.0.
- bpo-28643: Record profile-opt build progress with stamp files.
- bpo-31866: Finish removing support for AtheOS.

### Windows

- bpo-1102: Return `None` when `View.Fetch()` returns `ERROR_NO_MORE_ITEMS` instead of raising `MSIError`.

  Initial patch by Anthony Tuininga.

- bpo-31944: Fixes Modify button in Apps and Features dialog.

- bpo-20486: Implement the `Database.Close()` method to help closing MSI database objects.

- bpo-31857: Make the behavior of USE_STACKCHECK deterministic in a multi-threaded environment.

### macOS

- bpo-31392: Update macOS installer to use OpenSSL 1.0.2m

### IDLE

- bpo-32207: Improve tk event exception tracebacks in IDLE. When tk event handling is driven by IDLE’s run loop, a confusing and distracting queue.EMPTY traceback context is no longer added to tk event exception tracebacks. The traceback is now the same as when event handling is driven by user code. Patch based on a suggestion by Serhiy Storchaka.

- bpo-32164: Delete unused file idlelib/tabbedpages.py. Use of TabbedPageSet in configdialog was replaced by ttk.Notebook.

- bpo-32100: IDLE: Fix old and new bugs in pathbrowser; improve tests. Patch mostly by Cheryl Sabella.

- bpo-31858: IDLE – Restrict shell prompt manipulation to the shell. Editor and output windows only see an empty last prompt line. This simplifies the code and fixes a minor bug when newline is inserted. Sys.ps1, if present, is read on Shell start-up, but is not set or changed.

- bpo-31860: The font sample in the IDLE configuration dialog is now editable. Changes persist while IDLE remains open

- bpo-31836: Test_code_module now passes if run after test_idle, which sets ps1.

  The code module uses sys.ps1 if present or sets it to ‘>>> ‘ if not. Test_code_module now properly tests both behaviors. Ditto for ps2.

- bpo-28603: Fix a TypeError that caused a shell restart when printing a traceback that includes an exception that is unhashable. Patch by Zane Bitter.

- bpo-13802: Use non-Latin characters in the IDLE’s Font settings sample. Even if one selects a font that defines a limited subset of the unicode Basic Multilingual Plane, tcl/tk will use other fonts that define a character. The expanded example give users of non-Latin characters a better idea of what they might see in IDLE’s shell and editors.

  To make room for the expanded sample, frames on the Font tab are re-arranged. The Font/Tabs help explains a bit about the additions.

### Tools/Demos

- bpo-32159: Remove CVS and Subversion tools: remove svneol.py and treesync.py scripts. CPython migrated from CVS to Subversion, to Mercurial, and then to Git. CVS and Subversion are no longer used to develop CPython.

- bpo-30722: Make redemo work with Python 3.6 and newer versions.

  Also, remove the `LOCALE` option since it doesn’t work with string patterns in Python 3.

  Patch by Christoph Sarnowski.

### C API

- bpo-20891: Fix PyGILState_Ensure(). When PyGILState_Ensure() is called in a non-Python thread before PyEval_InitThreads(), only call PyEval_InitThreads() after calling PyThreadState_New() to fix a crash.
- bpo-32125: The `Py_UseClassExceptionsFlag` flag has been removed. It was deprecated and wasn’t used anymore since Python 2.0.
- bpo-25612: Move the current exception state from the frame object to the co-routine. This simplifies the interpreter and fixes a couple of obscure bugs caused by having swap exception state when entering or exiting a generator.
- bpo-23699: Add Py_RETURN_RICHCOMPARE macro to reduce boilerplate code in rich comparison functions.
- bpo-30697: The `PyExc_RecursionErrorInst` singleton is removed and `PyErr_NormalizeException()` does not use it anymore. This singleton is persistent and its members being never cleared may cause a segfault during finalization of the interpreter. See also bpo-22898.

## Python 3.7.0 alpha 2

Release date: 2017-10-16

### Core and Builtins

- bpo-31558: `gc.freeze()` is a new API that allows for moving all objects currently tracked by the garbage collector to a permanent generation, effectively removing them from future collection events. This can be used to protect those objects from having their PyGC_Head mutated. In effect, this enables great copy-on-write stability at fork().
- bpo-31642: Restored blocking “from package import module” by setting sys.modules[“package.module”] to None.
- bpo-31708: Allow use of asynchronous generator expressions in synchronous functions.
- bpo-31709: Drop support of asynchronous __aiter__.
- bpo-30404: The -u option now makes the stdout and stderr streams unbuffered rather than line-buffered.
- bpo-31619: Fixed a ValueError when convert a string with large number of underscores to integer with binary base.
- bpo-31602: Fix an assertion failure in `zipimporter.get_source()` in case of a bad `zlib.decompress()`. Patch by Oren Milman.
- bpo-31592: Fixed an assertion failure in Python parser in case of a bad `unicodedata.normalize()`. Patch by Oren Milman.
- bpo-31588: Raise a `TypeError` with a helpful error message when class creation fails due to a metaclass with a bad `__prepare__()` method. Patch by Oren Milman.
- bpo-31574: Importlib was instrumented with two dtrace probes to profile import timing.
- bpo-31566: Fix an assertion failure in `_warnings.warn()` in case of a bad `__name__` global. Patch by Oren Milman.
- bpo-31506: Improved the error message logic for object.__new__ and object.__init__.
- bpo-31505: Fix an assertion failure in `json`, in case `_json.make_encoder()` received a bad `encoder()` argument. Patch by Oren Milman.
- bpo-31492: Fix assertion failures in case of failing to import from a module with a bad `__name__` attribute, and in case of failing to access an attribute of such a module. Patch by Oren Milman.
- bpo-31478: Fix an assertion failure in `_random.Random.seed()` in case the argument has a bad `__abs__()` method. Patch by Oren Milman.
- bpo-31336: Speed up class creation by 10-20% by reducing the overhead in the necessary special method lookups. Patch by Stefan Behnel.
- bpo-31415: Add `-X importtime` option to show how long each import takes. It can be used to optimize application’s startup time. Support the `PYTHONPROFILEIMPORTTIME` as an equivalent way to enable this.
- bpo-31410: Optimized calling wrapper and classmethod descriptors.
- bpo-31353: PEP 553 - Add a new built-in called `breakpoint()` which calls `sys.breakpointhook()`. By default this imports `pdb` and calls `pdb.set_trace()`, but users may override `sys.breakpointhook()` to call whatever debugger they want. The original value of the hook is saved in `sys.__breakpointhook__`.
- bpo-17852: Maintain a list of open buffered files, flush them before exiting the interpreter. Based on a patch from Armin Rigo.
- bpo-31315: Fix an assertion failure in imp.create_dynamic(), when spec.name is not a string. Patch by Oren Milman.
- bpo-31311: Fix a crash in the `__setstate__()` method of `ctypes._CData`, in case of a bad `__dict__`. Patch by Oren Milman.
- bpo-31293: Fix crashes in true division and multiplication of a timedelta object by a float with a bad as_integer_ratio() method. Patch by Oren Milman.
- bpo-31285: Fix an assertion failure in `warnings.warn_explicit`, when the return value of the received loader’s get_source() has a bad splitlines() method. Patch by Oren Milman.
- bpo-30406: Make `async` and `await` proper keywords, as specified in PEP 492.

### Library

- bpo-30058: Fixed buffer overflow in select.kqueue.control().

- bpo-31672: `idpattern` in `string.Template` matched some non-ASCII characters. Now it uses `-i` regular expression local flag to avoid non-ASCII characters.

- bpo-31701: On Windows, faulthandler.enable() now ignores MSC and COM exceptions.

- bpo-31728: Prevent crashes in `_elementtree` due to unsafe cleanup of `Element.text` and `Element.tail`. Patch by Oren Milman.

- bpo-31671: Now `re.compile()` converts passed RegexFlag to normal int object before compiling. bm_regex_compile benchmark shows 14% performance improvements.

- bpo-30397: The types of compiled regular objects and match objects are now exposed as `re.Pattern` and `re.Match`. This adds information in pydoc output for the re module.

- bpo-31675: Fixed memory leaks in Tkinter’s methods splitlist() and split() when pass a string larger than 2 GiB.

- bpo-31673: Fixed typo in the name of Tkinter’s method adderrorinfo().

- bpo-31648: Improvements to path predicates in ElementTree:

  - Allow whitespace around predicate parts, i.e. “[a = ‘text’]” instead of requiring the less readable “[a=’text’]”.
  - Add support for text comparison of the current node, like “[.=’text’]”.

  Patch by Stefan Behnel.

- bpo-30806: Fix the string representation of a netrc object.

- bpo-31638: Add optional argument `compressed` to `zipapp.create_archive`, and add option `--compress` to the command line interface of `zipapp`.

- bpo-25351: Avoid venv activate failures with undefined variables

- bpo-20519: Avoid ctypes use (if possible) and improve import time for uuid.

- bpo-28293: The regular expression cache is no longer completely dumped when it is full.

- bpo-31596: Added pthread_getcpuclockid() to the time module

- bpo-27494: Make 2to3 accept a trailing comma in generator expressions. For example, `set(x for x in [],)` is now allowed.

- bpo-30347: Stop crashes when concurrently iterate over itertools.groupby() iterators.

- bpo-30346: An iterator produced by itertools.groupby() iterator now becomes exhausted after advancing the groupby iterator.

- bpo-31556: Cancel asyncio.wait_for future faster if timeout <= 0

- bpo-31540: Allow passing a context object in `concurrent.futures.ProcessPoolExecutor` constructor. Also, free job resources in `concurrent.futures.ProcessPoolExecutor` earlier to improve memory usage when a worker waits for new jobs.

- bpo-31516: `threading.current_thread()` should not return a dummy thread at shutdown.

- bpo-31525: In the sqlite module, require the sqlite3_prepare_v2 API. Thus, the sqlite module now requires sqlite version at least 3.3.9.

- bpo-26510: argparse subparsers are now required by default. This matches behaviour in Python 2. For optional subparsers, use the new parameter `add_subparsers(required=False)`. Patch by Anthony Sottile. (As of 3.7.0rc1, the default was changed to not required as had been the case since Python 3.3.)

- bpo-27541: Reprs of subclasses of some collection and iterator classes (`bytearray`, `array.array`, `collections.deque`, `collections.defaultdict`, `itertools.count`, `itertools.repeat`) now contain actual type name insteads of hardcoded name of the base class.

- bpo-31351: python -m ensurepip now exits with non-zero exit code if pip bootstrapping has failed.

- bpo-31389: `pdb.set_trace()` now takes an optional keyword-only argument `header`. If given, this is printed to the console just before debugging begins.

### Documentation

- bpo-31537: Fix incorrect usage of `get_history_length` in readline documentation example code. Patch by Brad Smith.
- bpo-30085: The operator functions without double underscores are preferred for clarity. The one with underscores are only kept for back-compatibility.

### Build

- bpo-31696: Improve compiler version information in `sys.version` when Python is built with Clang.
- bpo-31625: Stop using ranlib on static libraries. Instead, we assume ar supports the ‘s’ flag.
- bpo-31624: Remove support for BSD/OS.
- bpo-22140: Prevent double substitution of prefix in python-config.sh.
- bpo-31569: Correct PCBuild/ case to PCbuild/ in build scripts and documentation.
- bpo-31536: Avoid wholesale rebuild after `make regen-all` if nothing changed.

### IDLE

- bpo-31460: Simplify the API of IDLE’s Module Browser.

  Passing a widget instead of an flist with a root widget opens the option of creating a browser frame that is only part of a window. Passing a full file name instead of pieces assumed to come from a .py file opens the possibility of browsing python files that do not end in .py.

- bpo-31649: IDLE - Make _htest, _utest parameters keyword only.

- bpo-31559: Remove test order dependence in idle_test.test_browser.

- bpo-31459: Rename IDLE’s module browser from Class Browser to Module Browser. The original module-level class and method browser became a module browser, with the addition of module-level functions, years ago. Nested classes and functions were added yesterday. For back-compatibility, the virtual event <<open-class-browser>>, which appears on the Keys tab of the Settings dialog, is not changed. Patch by Cheryl Sabella.

- bpo-31500: Default fonts now are scaled on HiDPI displays.

- bpo-1612262: IDLE module browser now shows nested classes and functions. Original patches for code and tests by Guilherme Polo and Cheryl Sabella, respectively.

### C API

- bpo-28280: Make `PyMapping_Keys()`, `PyMapping_Values()` and `PyMapping_Items()` always return a `list` (rather than a `list` or a `tuple`). Patch by Oren Milman.
- bpo-31532: Fix memory corruption due to allocator mix in getpath.c between Py_GetPath() and Py_SetPath()
- bpo-25658: Implement PEP 539 for Thread Specific Storage (TSS) API: it is a new Thread Local Storage (TLS) API to CPython which would supersede use of the existing TLS API within the CPython interpreter, while deprecating the existing API. PEP written by Erik M. Bray, patch by Masayuki Yamamoto.

## Python 3.7.0 alpha 1

Release date: 2017-09-19

### Security

- bpo-29781: SSLObject.version() now correctly returns None when handshake over BIO has not been performed yet.
- bpo-29505: Add fuzz tests for float(str), int(str), unicode(str); for oss-fuzz.
- bpo-30947: Upgrade libexpat embedded copy from version 2.2.1 to 2.2.3 to get security fixes.
- bpo-30730: Prevent environment variables injection in subprocess on Windows. Prevent passing other environment variables and command arguments.
- bpo-30694: Upgrade expat copy from 2.2.0 to 2.2.1 to get fixes of multiple security vulnerabilities including: CVE-2017-9233 (External entity infinite loop DoS), CVE-2016-9063 (Integer overflow, re-fix), CVE-2016-0718 (Fix regression bugs from 2.2.0’s fix to CVE-2016-0718) and CVE-2012-0876 (Counter hash flooding with SipHash). Note: the CVE-2016-5300 (Use os-specific entropy sources like getrandom) doesn’t impact Python, since Python already gets entropy from the OS to set the expat secret using `XML_SetHashSalt()`.
- bpo-30500: Fix urllib.parse.splithost() to correctly parse fragments. For example, `splithost('//127.0.0.1#@evil.com/')` now correctly returns the `127.0.0.1` host, instead of treating `@evil.com` as the host in an authentication (`login@host`).
- bpo-29591: Update expat copy from 2.1.1 to 2.2.0 to get fixes of CVE-2016-0718 and CVE-2016-4472. See https://sourceforge.net/p/expat/bugs/537/ for more information.

### Core and Builtins

- bpo-31490: Fix an assertion failure in `ctypes` class definition, in case the class has an attribute whose name is specified in `_anonymous_` but not in `_fields_`. Patch by Oren Milman.

- bpo-31471: Fix an assertion failure in `subprocess.Popen()` on Windows, in case the env argument has a bad keys() method. Patch by Oren Milman.

- bpo-31418: Fix an assertion failure in `PyErr_WriteUnraisable()` in case of an exception with a bad `__module__` attribute. Patch by Oren Milman.

- bpo-31416: Fix assertion failures in case of a bad warnings.filters or warnings.defaultaction. Patch by Oren Milman.

- bpo-28411: Change direct usage of PyInterpreterState.modules to PyImport_GetModuleDict(). Also introduce more uniformity in other code that deals with sys.modules. This helps reduce complications when working on sys.modules.

- bpo-28411: Switch to the abstract API when dealing with `PyInterpreterState.modules`. This allows later support for all dict subclasses and other Mapping implementations. Also add a `PyImport_GetModule()` function to reduce a bunch of duplicated code.

- bpo-31411: Raise a TypeError instead of SystemError in case warnings.onceregistry is not a dictionary. Patch by Oren Milman.

- bpo-31344: For finer control of tracing behaviour when testing the interpreter, two new frame attributes have been added to control the emission of particular trace events: `f_trace_lines` (`True` by default) to turn off per-line trace events; and `f_trace_opcodes` (`False` by default) to turn on per-opcode trace events.

- bpo-31373: Fix several possible instances of undefined behavior due to floating-point demotions.

- bpo-30465: Location information (`lineno` and `col_offset`) in f-strings is now (mostly) correct. This fixes tools like flake8 from showing warnings on the wrong line (typically the first line of the file).

- bpo-30860: Consolidate CPython’s global runtime state under a single struct. This improves discoverability of the runtime state.

- bpo-31347: Fix possible undefined behavior in _PyObject_FastCall_Prepend.

- bpo-31343: Include sys/sysmacros.h for major(), minor(), and makedev(). GNU C libray plans to remove the functions from sys/types.h.

- bpo-31291: Fix an assertion failure in `zipimport.zipimporter.get_data` on Windows, when the return value of `pathname.replace('/','\\')` isn’t a string. Patch by Oren Milman.

- bpo-31271: Fix an assertion failure in the write() method of `io.TextIOWrapper`, when the encoder doesn’t return a bytes object. Patch by Oren Milman.

- bpo-31243: Fix a crash in some methods of `io.TextIOWrapper`, when the decoder’s state is invalid. Patch by Oren Milman.

- bpo-30721: `print` now shows correct usage hint for using Python 2 redirection syntax. Patch by Sanyam Khurana.

- bpo-31070: Fix a race condition in importlib _get_module_lock().

- bpo-30747: Add a non-dummy implementation of _Py_atomic_store and _Py_atomic_load on MSVC.

- bpo-31095: Fix potential crash during GC caused by `tp_dealloc` which doesn’t call `PyObject_GC_UnTrack()`.

- bpo-31071: Avoid masking original TypeError in call with * unpacking when other arguments are passed.

- bpo-30978: str.format_map() now passes key lookup exceptions through. Previously any exception was replaced with a KeyError exception.

- bpo-30808: Use _Py_atomic API for concurrency-sensitive signal state.

- bpo-30876: Relative import from unloaded package now reimports the package instead of failing with SystemError. Relative import from non-package now fails with ImportError rather than SystemError.

- bpo-30703: Improve signal delivery.

  Avoid using Py_AddPendingCall from signal handler, to avoid calling signal-unsafe functions. The tests I’m adding here fail without the rest of the patch, on Linux and OS X. This means our signal delivery logic had defects (some signals could be lost).

- bpo-30765: Avoid blocking in pthread_mutex_lock() when PyThread_acquire_lock() is asked not to block.

- bpo-31161: Make sure the ‘Missing parentheses’ syntax error message is only applied to SyntaxError, not to subclasses. Patch by Martijn Pieters.

- bpo-30814: Fixed a race condition when import a submodule from a package.

- bpo-30736: The internal unicodedata database has been upgraded to Unicode 10.0.

- bpo-30604: Move co_extra_freefuncs from per-thread to per-interpreter to avoid crashes.

- bpo-30597: `print` now shows expected input in custom error message when used as a Python 2 statement. Patch by Sanyam Khurana.

- bpo-30682: Removed a too-strict assertion that failed for certain f-strings, such as eval(“f’\n’”) and eval(“f’\r’”).

- bpo-30501: The compiler now produces more optimal code for complex condition expressions in the “if”, “while” and “assert” statement, the “if” expression, and generator expressions and comprehensions.

- bpo-28180: Implement PEP 538 (legacy C locale coercion). This means that when a suitable coercion target locale is available, both the core interpreter and locale-aware C extensions will assume the use of UTF-8 as the default text encoding, rather than ASCII.

- bpo-30486: Allows setting cell values for __closure__. Patch by Lisa Roach.

- bpo-30537: itertools.islice now accepts integer-like objects (having an __index__ method) as start, stop, and slice arguments

- bpo-25324: Tokens needed for parsing in Python moved to C. `COMMENT`, `NL` and `ENCODING`. This way the tokens and tok_names in the token module don’t get changed when you import the tokenize module.

- bpo-29104: Fixed parsing backslashes in f-strings.

- bpo-27945: Fixed various segfaults with dict when input collections are mutated during searching, inserting or comparing. Based on patches by Duane Griffin and Tim Mitchell.

- bpo-25794: Fixed type.__setattr__() and type.__delattr__() for non-interned attribute names. Based on patch by Eryk Sun.

- bpo-30039: If a KeyboardInterrupt happens when the interpreter is in the middle of resuming a chain of nested ‘yield from’ or ‘await’ calls, it’s now correctly delivered to the innermost frame.

- bpo-28974: `object.__format__(x, '')` is now equivalent to `str(x)` rather than `format(str(self), '')`.

- bpo-30024: Circular imports involving absolute imports with binding a submodule to a name are now supported.

- bpo-12414: sys.getsizeof() on a code object now returns the sizes which includes the code struct and sizes of objects which it references. Patch by Dong-hee Na.

- bpo-29839: len() now raises ValueError rather than OverflowError if __len__() returned a large negative integer.

- bpo-11913: README.rst is now included in the list of distutils standard READMEs and therefore included in source distributions.

- bpo-29914: Fixed default implementations of __reduce__ and __reduce_ex__(). object.__reduce__() no longer takes arguments, object.__reduce_ex__() now requires one argument.

- bpo-29949: Fix memory usage regression of set and frozenset object.

- bpo-29935: Fixed error messages in the index() method of tuple, list and deque when pass indices of wrong type.

- bpo-29816: Shift operation now has less opportunity to raise OverflowError. ValueError always is raised rather than OverflowError for negative counts. Shifting zero with non-negative count always returns zero.

- bpo-24821: Fixed the slowing down to 25 times in the searching of some unlucky Unicode characters.

- bpo-29102: Add a unique ID to PyInterpreterState. This makes it easier to identify each subinterpreter.

- bpo-29894: The deprecation warning is emitted if __complex__ returns an instance of a strict subclass of complex. In a future versions of Python this can be an error.

- bpo-29859: Show correct error messages when any of the pthread_* calls in thread_pthread.h fails.

- bpo-29849: Fix a memory leak when an ImportError is raised during from import.

- bpo-28856: Fix an oversight that %b format for bytes should support objects follow the buffer protocol.

- bpo-29723: The `sys.path[0]` initialization change for bpo-29139 caused a regression by revealing an inconsistency in how sys.path is initialized when executing `__main__` from a zipfile, directory, or other import location. The interpreter now consistently avoids ever adding the import location’s parent directory to `sys.path`, and ensures no other `sys.path` entries are inadvertently modified when inserting the import location named on the command line.

- bpo-29568: Escaped percent “%%” in the format string for classic string formatting no longer allows any characters between two percents.

- bpo-29714: Fix a regression that bytes format may fail when containing zero bytes inside.

- bpo-29695: bool(), float(), list() and tuple() no longer take keyword arguments. The first argument of int() can now be passes only as positional argument.

- bpo-28893: Set correct __cause__ for errors about invalid awaitables returned from __aiter__ and __anext__.

- bpo-28876: `bool(range)` works even if `len(range)` raises `OverflowError`.

- bpo-29683: Fixes to memory allocation in _PyCode_SetExtra. Patch by Brian Coleman.

- bpo-29684: Fix minor regression of PyEval_CallObjectWithKeywords. It should raise TypeError when kwargs is not a dict. But it might cause segv when args=NULL and kwargs is not a dict.

- bpo-28598: Support __rmod__ for subclasses of str being called before str.__mod__. Patch by Martijn Pieters.

- bpo-29607: Fix stack_effect computation for CALL_FUNCTION_EX. Patch by Matthieu Dartiailh.

- bpo-29602: Fix incorrect handling of signed zeros in complex constructor for complex subclasses and for inputs having a __complex__ method. Patch by Serhiy Storchaka.

- bpo-29347: Fixed possibly dereferencing undefined pointers when creating weakref objects.

- bpo-29463: Add `docstring` field to Module, ClassDef, FunctionDef, and AsyncFunctionDef ast nodes. docstring is not first stmt in their body anymore. It affects `co_firstlineno` and `co_lnotab` of code object for module and class. (Reverted in bpo-32911.)

- bpo-29438: Fixed use-after-free problem in key sharing dict.

- bpo-29546: Set the ‘path’ and ‘name’ attribute on ImportError for `from ... import ...`.

- bpo-29546: Improve from-import error message with location

- bpo-29478: If max_line_length=None is specified while using the Compat32 policy, it is no longer ignored. Patch by Mircea Cosbuc.

- bpo-29319: Prevent RunMainFromImporter overwriting sys.path[0].

- bpo-29337: Fixed possible BytesWarning when compare the code objects. Warnings could be emitted at compile time.

- bpo-29327: Fixed a crash when pass the iterable keyword argument to sorted().

- bpo-29034: Fix memory leak and use-after-free in os module (path_converter).

- bpo-29159: Fix regression in bytes(x) when x.__index__() raises Exception.

- bpo-29049: Call _PyObject_GC_TRACK() lazily when calling Python function. Calling function is up to 5% faster.

- bpo-28927: bytes.fromhex() and bytearray.fromhex() now ignore all ASCII whitespace, not only spaces. Patch by Robert Xiao.

- bpo-28932: Do not include <sys/random.h> if it does not exist.

- bpo-25677: Correct the positioning of the syntax error caret for indented blocks. Based on patch by Michael Layzell.

- bpo-29000: Fixed bytes formatting of octals with zero padding in alternate form.

- bpo-18896: Python function can now have more than 255 parameters. collections.namedtuple() now supports tuples with more than 255 elements.

- bpo-28596: The preferred encoding is UTF-8 on Android. Patch written by Chi Hsuan Yen.

- bpo-22257: Clean up interpreter startup (see PEP 432).

- bpo-26919: On Android, operating system data is now always encoded/decoded to/from UTF-8, instead of the locale encoding to avoid inconsistencies with os.fsencode() and os.fsdecode() which are already using UTF-8.

- bpo-28991: functools.lru_cache() was susceptible to an obscure reentrancy bug triggerable by a monkey-patched len() function.

- bpo-28147: Fix a memory leak in split-table dictionaries: setattr() must not convert combined table into split table. Patch written by INADA Naoki.

- bpo-28739: f-string expressions are no longer accepted as docstrings and by ast.literal_eval() even if they do not include expressions.

- bpo-28512: Fixed setting the offset attribute of SyntaxError by PyErr_SyntaxLocationEx() and PyErr_SyntaxLocationObject().

- bpo-28918: Fix the cross compilation of xxlimited when Python has been built with Py_DEBUG defined.

- bpo-23722: Rather than silently producing a class that doesn’t support zero-argument `super()` in methods, failing to pass the new `__classcell__` namespace entry up to `type.__new__` now results in a `DeprecationWarning` and a class that supports zero-argument `super()`.

- bpo-28797: Modifying the class __dict__ inside the __set_name__ method of a descriptor that is used inside that class no longer prevents calling the __set_name__ method of other descriptors.

- bpo-28799: Remove the `PyEval_GetCallStats()` function and deprecate the untested and undocumented `sys.callstats()` function. Remove the `CALL_PROFILE` special build: use the `sys.setprofile()` function, `cProfile` or `profile` to profile function calls.

- bpo-12844: More than 255 arguments can now be passed to a function.

- bpo-28782: Fix a bug in the implementation `yield from` when checking if the next instruction is YIELD_FROM. Regression introduced by WORDCODE (bpo-26647).

- bpo-28774: Fix error position of the unicode error in ASCII and Latin1 encoders when a string returned by the error handler contains multiple non-encodable characters (non-ASCII for the ASCII codec, characters out of the U+0000-U+00FF range for Latin1).

- bpo-28731: Optimize _PyDict_NewPresized() to create correct size dict. Improve speed of dict literal with constant keys up to 30%.

- bpo-28532: Show sys.version when -V option is supplied twice.

- bpo-27100: The with-statement now checks for __enter__ before it checks for __exit__. This gives less confusing error messages when both methods are missing. Patch by Jonathan Ellington.

- bpo-28746: Fix the set_inheritable() file descriptor method on platforms that do not have the ioctl FIOCLEX and FIONCLEX commands.

- bpo-26920: Fix not getting the locale’s charset upon initializing the interpreter, on platforms that do not have langinfo.

- bpo-28648: Fixed crash in Py_DecodeLocale() in debug build on Mac OS X when decode astral characters. Patch by Xiang Zhang.

- bpo-28665: Improve speed of the STORE_DEREF opcode by 40%.

- bpo-19398: Extra slash no longer added to sys.path components in case of empty compile-time PYTHONPATH components.

- bpo-28621: Sped up converting int to float by reusing faster bits counting implementation. Patch by Adrian Wielgosik.

- bpo-28580: Optimize iterating split table values. Patch by Xiang Zhang.

- bpo-28583: PyDict_SetDefault didn’t combine split table when needed. Patch by Xiang Zhang.

- bpo-28128: Deprecation warning for invalid str and byte escape sequences now prints better information about where the error occurs. Patch by Serhiy Storchaka and Eric Smith.

- bpo-28509: dict.update() no longer allocate unnecessary large memory.

- bpo-28426: Fixed potential crash in PyUnicode_AsDecodedObject() in debug build.

- bpo-28517: Fixed of-by-one error in the peephole optimizer that caused keeping unreachable code.

- bpo-28214: Improved exception reporting for problematic __set_name__ attributes.

- bpo-23782: Fixed possible memory leak in _PyTraceback_Add() and exception loss in PyTraceBack_Here().

- bpo-28183: Optimize and cleanup dict iteration.

- bpo-26081: Added C implementation of asyncio.Future. Original patch by Yury Selivanov.

- bpo-28379: Added sanity checks and tests for PyUnicode_CopyCharacters(). Patch by Xiang Zhang.

- bpo-28376: The type of long range iterator is now registered as Iterator. Patch by Oren Milman.

- bpo-28376: Creating instances of range_iterator by calling range_iterator type now is disallowed. Calling iter() on range instance is the only way. Patch by Oren Milman.

- bpo-26906: Resolving special methods of uninitialized type now causes implicit initialization of the type instead of a fail.

- bpo-18287: PyType_Ready() now checks that tp_name is not NULL. Original patch by Niklas Koep.

- bpo-24098: Fixed possible crash when AST is changed in process of compiling it.

- bpo-28201: Dict reduces possibility of 2nd conflict in hash table when hashes have same lower bits.

- bpo-28350: String constants with null character no longer interned.

- bpo-26617: Fix crash when GC runs during weakref callbacks.

- bpo-27942: String constants now interned recursively in tuples and frozensets.

- bpo-28289: ImportError.__init__ now resets not specified attributes.

- bpo-21578: Fixed misleading error message when ImportError called with invalid keyword args.

- bpo-28203: Fix incorrect type in complex(1.0, {2:3}) error message. Patch by Soumya Sharma.

- bpo-28086: Single var-positional argument of tuple subtype was passed unscathed to the C-defined function. Now it is converted to exact tuple.

- bpo-28214: Now __set_name__ is looked up on the class instead of the instance.

- bpo-27955: Fallback on reading /dev/urandom device when the getrandom() syscall fails with EPERM, for example when blocked by SECCOMP.

- bpo-28192: Don’t import readline in isolated mode.

- bpo-27441: Remove some redundant assignments to ob_size in longobject.c. Thanks Oren Milman.

- bpo-27222: Clean up redundant code in long_rshift function. Thanks Oren Milman.

- Upgrade internal unicode databases to Unicode version 9.0.0.

- bpo-28131: Fix a regression in zipimport’s compile_source(). zipimport should use the same optimization level as the interpreter.

- bpo-28126: Replace Py_MEMCPY with memcpy(). Visual Studio can properly optimize memcpy().

- bpo-28120: Fix dict.pop() for splitted dictionary when trying to remove a “pending key” (Not yet inserted in split-table). Patch by Xiang Zhang.

- bpo-26182: Raise DeprecationWarning when async and await keywords are used as variable/attribute/class/function name.

- bpo-26182: Fix a refleak in code that raises DeprecationWarning.

- bpo-28721: Fix asynchronous generators aclose() and athrow() to handle StopAsyncIteration propagation properly.

- bpo-26110: Speed-up method calls: add LOAD_METHOD and CALL_METHOD opcodes.

### Library

- bpo-31499: xml.etree: Fix a crash when a parser is part of a reference cycle.

- bpo-31482: `random.seed()` now works with bytes in version=1

- bpo-28556: typing.get_type_hints now finds the right globalns for classes and modules by default (when no `globalns` was specified by the caller).

- bpo-28556: Speed improvements to the `typing` module. Original PRs by Ivan Levkivskyi and Mitar.

- bpo-31544: The C accelerator module of ElementTree ignored exceptions raised when looking up TreeBuilder target methods in XMLParser().

- bpo-31234: socket.create_connection() now fixes manually a reference cycle: clear the variable storing the last exception on success.

- bpo-31457: LoggerAdapter objects can now be nested.

- bpo-31431: SSLContext.check_hostname now automatically sets SSLContext.verify_mode to ssl.CERT_REQUIRED instead of failing with a ValueError.

- bpo-31233: socketserver.ThreadingMixIn now keeps a list of non-daemonic threads to wait until all these threads complete in server_close().

- bpo-28638: Changed the implementation strategy for collections.namedtuple() to substantially reduce the use of exec() in favor of precomputed methods. As a result, the verbose parameter and _source attribute are no longer supported. The benefits include 1) having a smaller memory footprint for applications using multiple named tuples, 2) faster creation of the named tuple class (approx 4x to 6x depending on how it is measured), and 3) minor speed-ups for instance creation using __new__, _make, and _replace. (The primary patch contributor is Jelle Zijlstra with further improvements by INADA Naoki, Serhiy Storchaka, and Raymond Hettinger.)

- bpo-31400: Improves SSL error handling to avoid losing error numbers.

- bpo-27629: Make return types of SSLContext.wrap_bio() and SSLContext.wrap_socket() customizable.

- bpo-28958: ssl.SSLContext() now uses OpenSSL error information when a context cannot be instantiated.

- bpo-28182: The SSL module now raises SSLCertVerificationError when OpenSSL fails to verify the peer’s certificate. The exception contains more information about the error.

- bpo-27340: SSLSocket.sendall() now uses memoryview to create slices of data. This fixes support for all bytes-like object. It is also more efficient and avoids costly copies.

- bpo-14191: A new function `argparse.ArgumentParser.parse_intermixed_args` provides the ability to parse command lines where there user intermixes options and positional arguments.

- bpo-31178: Fix string concatenation bug in rare error path in the subprocess module

- bpo-31350: Micro-optimize `asyncio._get_running_loop()` to become up to 10% faster.

- bpo-31170: expat: Update libexpat from 2.2.3 to 2.2.4. Fix copying of partial characters for UTF-8 input (libexpat bug 115): https://github.com/libexpat/libexpat/issues/115

- bpo-29136: Add TLS 1.3 cipher suites and OP_NO_TLSv1_3.

- bpo-1198569: `string.Template` subclasses can optionally define `braceidpattern` if they want to specify different placeholder patterns inside and outside the braces. If None (the default) it falls back to `idpattern`.

- bpo-31326: concurrent.futures.ProcessPoolExecutor.shutdown() now explicitly closes the call queue. Moreover, shutdown(wait=True) now also join the call queue thread, to prevent leaking a dangling thread.

- bpo-27144: The `map()` and `as_completed()` iterators in `concurrent.futures` now avoid keeping a reference to yielded objects.

- bpo-31281: Fix `fileinput.FileInput(files, inplace=True)` when `files` contain `pathlib.Path` objects.

- bpo-10746: Fix ctypes producing wrong PEP 3118 type codes for integer types.

- bpo-27584: `AF_VSOCK` has been added to the socket interface which allows communication between virtual machines and their host.

- bpo-22536: The subprocess module now sets the filename when FileNotFoundError is raised on POSIX systems due to the executable or cwd not being found.

- bpo-29741: Update some methods in the _pyio module to also accept integer types. Patch by Oren Milman.

- bpo-31249: concurrent.futures: WorkItem.run() used by ThreadPoolExecutor now breaks a reference cycle between an exception object and the WorkItem object.

- bpo-31247: xmlrpc.server now explicitly breaks reference cycles when using sys.exc_info() in code handling exceptions.

- bpo-23835: configparser: reading defaults in the `ConfigParser()` constructor is now using `read_dict()`, making its behavior consistent with the rest of the parser. Non-string keys and values in the defaults dictionary are now being implicitly converted to strings. Patch by James Tocknell.

- bpo-31238: pydoc: the stop() method of the private ServerThread class now waits until DocServer.serve_until_quit() completes and then explicitly sets its docserver attribute to None to break a reference cycle.

- bpo-5001: Many asserts in `multiprocessing` are now more informative, and some error types have been changed to more specific ones.

- bpo-31109: Convert zipimport to use Argument Clinic.

- bpo-30102: The ssl and hashlib modules now call OPENSSL_add_all_algorithms_noconf() on OpenSSL < 1.1.0. The function detects CPU features and enables optimizations on some CPU architectures such as POWER8. Patch is based on research from Gustavo Serra Scalet.

- bpo-18966: Non-daemonic threads created by a multiprocessing.Process are now joined on child exit.

- bpo-31183: `dis` now works with asynchronous generator and coroutine objects. Patch by George Collins based on diagnosis by Luciano Ramalho.

- bpo-5001: There are a number of uninformative asserts in the `multiprocessing` module, as noted in issue 5001. This change fixes two of the most potentially problematic ones, since they are in error-reporting code, in the `multiprocessing.managers.convert_to_error` function. (It also makes more informative a ValueError message.) The only potentially problematic change is that the AssertionError is now a TypeError; however, this should also help distinguish it from an AssertionError being reported by the function/its caller (such as in issue 31169). - Patch by Allen W. Smith (drallensmith on github).

- bpo-31185: Fixed miscellaneous errors in asyncio speedup module.

- bpo-31151: socketserver.ForkingMixIn.server_close() now waits until all child processes completed to prevent leaking zombie processes.

- bpo-31072: Add an `include_file` parameter to `zipapp.create_archive()`

- bpo-24700: Optimize array.array comparison. It is now from 10x up to 70x faster when comparing arrays holding values of the same integer type.

- bpo-31135: ttk: fix the destroy() method of LabeledScale and OptionMenu classes. Call the parent destroy() method even if the used attribute doesn’t exist. The LabeledScale.destroy() method now also explicitly clears label and scale attributes to help the garbage collector to destroy all widgets.

- bpo-31107: Fix `copyreg._slotnames()` mangled attribute calculation for classes whose name begins with an underscore. Patch by Shane Harvey.

- bpo-31080: Allow `logging.config.fileConfig` to accept kwargs and/or args.

- bpo-30897: `pathlib.Path` objects now include an `is_mount()` method (only implemented on POSIX). This is similar to `os.path.ismount(p)`. Patch by Cooper Ry Lees.

- bpo-31061: Fixed a crash when using asyncio and threads.

- bpo-30987: Added support for CAN ISO-TP protocol in the socket module.

- bpo-30522: Added a `setStream` method to `logging.StreamHandler` to allow the stream to be set after creation.

- bpo-30502: Fix handling of long oids in ssl. Based on patch by Christian Heimes.

- bpo-5288: Support tzinfo objects with sub-minute offsets.

- bpo-30919: Fix shared memory performance regression in multiprocessing in 3.x.

  Shared memory used anonymous memory mappings in 2.x, while 3.x mmaps actual files. Try to be careful to do as little disk I/O as possible.

- bpo-26732: Fix too many fds in processes started with the “forkserver” method.

  A child process would inherit as many fds as the number of still-running children.

- bpo-29403: Fix `unittest.mock`’s autospec to not fail on method-bound builtin functions. Patch by Aaron Gallagher.

- bpo-30961: Fix decrementing a borrowed reference in tracemalloc.

- bpo-19896: Fix multiprocessing.sharedctypes to recognize typecodes `'q'` and `'Q'`.

- bpo-30946: Remove obsolete code in readline module for platforms where GNU readline is older than 2.1 or where select() is not available.

- bpo-25684: Change `ttk.OptionMenu` radiobuttons to be unique across instances of `OptionMenu`.

- bpo-30886: Fix multiprocessing.Queue.join_thread(): it now waits until the thread completes, even if the thread was started by the same process which created the queue.

- bpo-29854: Fix segfault in readline when using readline’s history-size option. Patch by Nir Soffer.

- bpo-30794: Added multiprocessing.Process.kill method to terminate using the SIGKILL signal on Unix.

- bpo-30319: socket.close() now ignores ECONNRESET error.

- bpo-30828: Fix out of bounds write in `asyncio.CFuture.remove_done_callback()`.

- bpo-30302: Use keywords in the `repr` of `datetime.timedelta`.

- bpo-30807: signal.setitimer() may disable the timer when passed a tiny value.

  Tiny values (such as 1e-6) are valid non-zero values for setitimer(), which is specified as taking microsecond-resolution intervals. However, on some platform, our conversion routine could convert 1e-6 into a zero interval, therefore disabling the timer instead of (re-)scheduling it.

- bpo-30441: Fix bug when modifying os.environ while iterating over it

- bpo-29585: Avoid importing `sysconfig` from `site` to improve startup speed. Python startup is about 5% faster on Linux and 30% faster on macOS.

- bpo-29293: Add missing parameter “n” on multiprocessing.Condition.notify().

  The doc claims multiprocessing.Condition behaves like threading.Condition, but its notify() method lacked the optional “n” argument (to specify the number of sleepers to wake up) that threading.Condition.notify() accepts.

- bpo-30532: Fix email header value parser dropping folding white space in certain cases.

- bpo-30596: Add a `close()` method to `multiprocessing.Process`.

- bpo-9146: Fix a segmentation fault in _hashopenssl when standard hash functions such as md5 are not available in the linked OpenSSL library. As in some special FIPS-140 build environments.

- bpo-29169: Update zlib to 1.2.11.

- bpo-30119: ftplib.FTP.putline() now throws ValueError on commands that contains CR or LF. Patch by Dong-hee Na.

- bpo-30879: os.listdir() and os.scandir() now emit bytes names when called with bytes-like argument.

- bpo-30746: Prohibited the ‘=’ character in environment variable names in `os.putenv()` and `os.spawn*()`.

- bpo-30664: The description of a unittest subtest now preserves the order of keyword arguments of TestCase.subTest().

- bpo-21071: struct.Struct.format type is now `str` instead of `bytes`.

- bpo-29212: Fix concurrent.futures.thread.ThreadPoolExecutor threads to have a non repr() based thread name by default when no thread_name_prefix is supplied. They will now identify themselves as “ThreadPoolExecutor-y_n”.

- bpo-29755: Fixed the lgettext() family of functions in the gettext module. They now always return bytes.

- bpo-30616: Functional API of enum allows to create empty enums. Patched by Dong-hee Na

- bpo-30038: Fix race condition between signal delivery and wakeup file descriptor. Patch by Nathaniel Smith.

- bpo-23894: lib2to3 now recognizes `rb'...'` and `f'...'` strings.

- bpo-24744: pkgutil.walk_packages function now raises ValueError if path is a string. Patch by Sanyam Khurana.

- bpo-24484: Avoid race condition in multiprocessing cleanup.

- bpo-30589: Fix multiprocessing.Process.exitcode to return the opposite of the signal number when the process is killed by a signal (instead of 255) when using the “forkserver” method.

- bpo-28994: The traceback no longer displayed for SystemExit raised in a callback registered by atexit.

- bpo-30508: Don’t log exceptions if Task/Future “cancel()” method was called.

- bpo-30645: Fix path calculation in `imp.load_package()`, fixing it for cases when a package is only shipped with bytecodes. Patch by Alexandru Ardelean.

- bpo-11822: The dis.dis() function now is able to disassemble nested code objects.

- bpo-30624: selectors does not take KeyboardInterrupt and SystemExit into account, leaving a fd in a bad state in case of error. Patch by Giampaolo Rodola’.

- bpo-30595: multiprocessing.Queue.get() with a timeout now polls its reader in non-blocking mode if it succeeded to acquire the lock but the acquire took longer than the timeout.

- bpo-28556: Updates to typing module: Add generic AsyncContextManager, add support for ContextManager on all versions. Original PRs by Jelle Zijlstra and Ivan Levkivskyi

- bpo-30605: re.compile() no longer raises a BytesWarning when compiling a bytes instance with misplaced inline modifier. Patch by Roy Williams.

- bpo-29870: Fix ssl sockets leaks when connection is aborted in asyncio/ssl implementation. Patch by Michaël Sghaïer.

- bpo-29743: Closing transport during handshake process leaks open socket. Patch by Nikolay Kim

- bpo-27585: Fix waiter cancellation in asyncio.Lock. Patch by Mathieu Sornay.

- bpo-30014: modify() method of poll(), epoll() and devpoll() based classes of selectors module is around 10% faster. Patch by Giampaolo Rodola’.

- bpo-30418: On Windows, subprocess.Popen.communicate() now also ignore EINVAL on stdin.write() if the child process is still running but closed the pipe.

- bpo-30463: Addded empty __slots__ to abc.ABC. This allows subclassers to deny __dict__ and __weakref__ creation. Patch by Aaron Hall.

- bpo-30520: Loggers are now pickleable.

- bpo-30557: faulthandler now correctly filters and displays exception codes on Windows

- bpo-30526: Add TextIOWrapper.reconfigure() and a TextIOWrapper.write_through attribute.

- bpo-30245: Fix possible overflow when organize struct.pack_into error message. Patch by Yuan Liu.

- bpo-30378: Fix the problem that logging.handlers.SysLogHandler cannot handle IPv6 addresses.

- bpo-16500: Allow registering at-fork handlers.

- bpo-30470: Deprecate invalid ctypes call protection on Windows. Patch by Mariatta Wijaya.

- bpo-30414: multiprocessing.Queue._feed background running thread do not break from main loop on exception.

- bpo-30003: Fix handling escape characters in HZ codec. Based on patch by Ma Lin.

- bpo-30149: inspect.signature() now supports callables with variable-argument parameters wrapped with partialmethod. Patch by Dong-hee Na.

- bpo-30436: importlib.find_spec() raises ModuleNotFoundError instead of AttributeError if the specified parent module is not a package (i.e. lacks a __path__ attribute).

- bpo-30301: Fix AttributeError when using SimpleQueue.empty() under spawn and forkserver start methods.

- bpo-30375: Warnings emitted when compile a regular expression now always point to the line in the user code. Previously they could point into inners of the re module if emitted from inside of groups or conditionals.

- bpo-30329: imaplib and poplib now catch the Windows socket WSAEINVAL error (code 10022) on shutdown(SHUT_RDWR): An invalid operation was attempted. This error occurs sometimes on SSL connections.

- bpo-29196: Removed previously deprecated in Python 2.4 classes Plist, Dict and _InternalDict in the plistlib module. Dict values in the result of functions readPlist() and readPlistFromBytes() are now normal dicts. You no longer can use attribute access to access items of these dictionaries.

- bpo-9850: The `macpath` is now deprecated and will be removed in Python 3.8.

- bpo-30299: Compiling regular expression in debug mode on CPython now displays the compiled bytecode in human readable form.

- bpo-30048: Fixed `Task.cancel()` can be ignored when the task is running coroutine and the coroutine returned without any more `await`.

- bpo-30266: contextlib.AbstractContextManager now supports anti-registration by setting __enter__ = None or __exit__ = None, following the pattern introduced in bpo-25958. Patch by Jelle Zijlstra.

- bpo-30340: Enhanced regular expressions optimization. This increased the performance of matching some patterns up to 25 times.

- bpo-30298: Weaken the condition of deprecation warnings for inline modifiers. Now allowed several subsequential inline modifiers at the start of the pattern (e.g. `'(?i)(?s)...'`). In verbose mode whitespaces and comments now are allowed before and between inline modifiers (e.g. `'(?x) (?i) (?s)...'`).

- bpo-30285: Optimized case-insensitive matching and searching of regular expressions.

- bpo-29990: Fix range checking in GB18030 decoder. Original patch by Ma Lin.

- bpo-29979: rewrite cgi.parse_multipart, reusing the FieldStorage class and making its results consistent with those of FieldStorage for multipart/form-data requests. Patch by Pierre Quentel.

- bpo-30243: Removed the __init__ methods of _json’s scanner and encoder. Misusing them could cause memory leaks or crashes. Now scanner and encoder objects are completely initialized in the __new__ methods.

- bpo-30215: Compiled regular expression objects with the re.LOCALE flag no longer depend on the locale at compile time. Only the locale at matching time affects the result of matching.

- bpo-30185: Avoid KeyboardInterrupt tracebacks in forkserver helper process when Ctrl-C is received.

- bpo-30103: binascii.b2a_uu() and uu.encode() now support using `'`'` as zero instead of space.

- bpo-28556: Various updates to typing module: add typing.NoReturn type, use WrapperDescriptorType, minor bug-fixes. Original PRs by Jim Fasarakis-Hilliard and Ivan Levkivskyi.

- bpo-30205: Fix getsockname() for unbound AF_UNIX sockets on Linux.

- bpo-30228: The seek() and tell() methods of io.FileIO now set the internal seekable attribute to avoid one syscall on open() (in buffered or text mode).

- bpo-30190: unittest’s assertAlmostEqual and assertNotAlmostEqual provide a better message in case of failure which includes the difference between left and right arguments. (patch by Giampaolo Rodola’)

- bpo-30101: Add support for curses.A_ITALIC.

- bpo-29822: inspect.isabstract() now works during __init_subclass__. Patch by Nate Soares.

- bpo-29960: Preserve generator state when _random.Random.setstate() raises an exception. Patch by Bryan Olson.

- bpo-30070: Fixed leaks and crashes in errors handling in the parser module.

- bpo-22352: Column widths in the output of dis.dis() are now adjusted for large line numbers and instruction offsets.

- bpo-30061: Fixed crashes in IOBase methods __next__() and readlines() when readline() or __next__() respectively return non-sizeable object. Fixed possible other errors caused by not checking results of PyObject_Size(), PySequence_Size(), or PyMapping_Size().

- bpo-30218: Fix PathLike support for shutil.unpack_archive. Patch by Jelle Zijlstra.

- bpo-10076: Compiled regular expression and match objects in the re module now support copy.copy() and copy.deepcopy() (they are considered atomic).

- bpo-30068: _io._IOBase.readlines will check if it’s closed first when hint is present.

- bpo-29694: Fixed race condition in pathlib mkdir with flags parents=True. Patch by Armin Rigo.

- bpo-29692: Fixed arbitrary unchaining of RuntimeError exceptions in contextlib.contextmanager. Patch by Siddharth Velankar.

- bpo-26187: Test that sqlite3 trace callback is not called multiple times when schema is changing. Indirectly fixed by switching to use sqlite3_prepare_v2() in bpo-9303. Patch by Aviv Palivoda.

- bpo-30017: Allowed calling the close() method of the zip entry writer object multiple times. Writing to a closed writer now always produces a ValueError.

- bpo-29998: Pickling and copying ImportError now preserves name and path attributes.

- bpo-29995: re.escape() now escapes only regex special characters.

- bpo-29962: Add math.remainder operation, implementing remainder as specified in IEEE 754.

- bpo-29649: Improve struct.pack_into() exception messages for problems with the buffer size and offset. Patch by Andrew Nester.

- bpo-29654: Support If-Modified-Since HTTP header (browser cache). Patch by Pierre Quentel.

- bpo-29931: Fixed comparison check for ipaddress.ip_interface objects. Patch by Sanjay Sundaresan.

- bpo-29953: Fixed memory leaks in the replace() method of datetime and time objects when pass out of bound fold argument.

- bpo-29942: Fix a crash in itertools.chain.from_iterable when encountering long runs of empty iterables.

- bpo-10030: Sped up reading encrypted ZIP files by 2 times.

- bpo-29204: Element.getiterator() and the html parameter of XMLParser() were deprecated only in the documentation (since Python 3.2 and 3.4 correspondintly). Now using them emits a deprecation warning.

- bpo-27863: Fixed multiple crashes in ElementTree caused by race conditions and wrong types.

- bpo-25996: Added support of file descriptors in os.scandir() on Unix. os.fwalk() is sped up by 2 times by using os.scandir().

- bpo-28699: Fixed a bug in pools in multiprocessing.pool that raising an exception at the very first of an iterable may swallow the exception or make the program hang. Patch by Davin Potts and Xiang Zhang.

- bpo-23890: unittest.TestCase.assertRaises() now manually breaks a reference cycle to not keep objects alive longer than expected.

- bpo-29901: The zipapp module now supports general path-like objects, not just pathlib.Path.

- bpo-25803: Avoid incorrect errors raised by Path.mkdir(exist_ok=True) when the OS gives priority to errors such as EACCES over EEXIST.

- bpo-29861: Release references to tasks, their arguments and their results as soon as they are finished in multiprocessing.Pool.

- bpo-19930: The mode argument of os.makedirs() no longer affects the file permission bits of newly-created intermediate-level directories.

- bpo-29884: faulthandler: Restore the old sigaltstack during teardown. Patch by Christophe Zeitouny.

- bpo-25455: Fixed crashes in repr of recursive buffered file-like objects.

- bpo-29800: Fix crashes in partial.__repr__ if the keys of partial.keywords are not strings. Patch by Michael Seifert.

- bpo-8256: Fixed possible failing or crashing input() if attributes “encoding” or “errors” of sys.stdin or sys.stdout are not set or are not strings.

- bpo-28692: Using non-integer value for selecting a plural form in gettext is now deprecated.

- bpo-26121: Use C library implementation for math functions erf() and erfc().

- bpo-29619: os.stat() and os.DirEntry.inode() now convert inode (st_ino) using unsigned integers.

- bpo-28298: Fix a bug that prevented array ‘Q’, ‘L’ and ‘I’ from accepting big intables (objects that have __int__) as elements.

- bpo-29645: Speed up importing the webbrowser module. webbrowser.register() is now thread-safe.

- bpo-28231: The zipfile module now accepts path-like objects for external paths.

- bpo-26915: index() and count() methods of collections.abc.Sequence now check identity before checking equality when do comparisons.

- bpo-28682: Added support for bytes paths in os.fwalk().

- bpo-29728: Add new `socket.TCP_NOTSENT_LOWAT` (Linux 3.12) constant. Patch by Nathaniel J. Smith.

- bpo-29623: Allow use of path-like object as a single argument in ConfigParser.read(). Patch by David Ellis.

- bpo-9303: Migrate sqlite3 module to _v2 API. Patch by Aviv Palivoda.

- bpo-28963: Fix out of bound iteration in asyncio.Future.remove_done_callback implemented in C.

- bpo-29704: asyncio.subprocess.SubprocessStreamProtocol no longer closes before all pipes are closed.

- bpo-29271: Fix Task.current_task and Task.all_tasks implemented in C to accept None argument as their pure Python implementation.

- bpo-29703: Fix asyncio to support instantiation of new event loops in child processes.

- bpo-29615: SimpleXMLRPCDispatcher no longer chains KeyError (or any other exception) to exception(s) raised in the dispatched methods. Patch by Petr Motejlek.

- bpo-7769: Method register_function() of xmlrpc.server.SimpleXMLRPCDispatcher and its subclasses can now be used as a decorator.

- bpo-29376: Fix assertion error in threading._DummyThread.is_alive().

- bpo-28624: Add a test that checks that cwd parameter of Popen() accepts PathLike objects. Patch by Sayan Chowdhury.

- bpo-28518: Start a transaction implicitly before a DML statement. Patch by Aviv Palivoda.

- bpo-29742: get_extra_info() raises exception if get called on closed ssl transport. Patch by Nikolay Kim.

- bpo-16285: urllib.parse.quote is now based on RFC 3986 and hence includes ‘~’ in the set of characters that is not quoted by default. Patch by Christian Theune and Ratnadeep Debnath.

- bpo-29532: Altering a kwarg dictionary passed to functools.partial() no longer affects a partial object after creation.

- bpo-29110: Fix file object leak in aifc.open() when file is given as a filesystem path and is not in valid AIFF format. Patch by Anthony Zhang.

- bpo-22807: Add uuid.SafeUUID and uuid.UUID.is_safe to relay information from the platform about whether generated UUIDs are generated with a multiprocessing safe method.

- bpo-29576: Improve some deprecations in importlib. Some deprecated methods now emit DeprecationWarnings and have better descriptive messages.

- bpo-29534: Fixed different behaviour of Decimal.from_float() for _decimal and _pydecimal. Thanks Andrew Nester.

- bpo-10379: locale.format_string now supports the ‘monetary’ keyword argument, and locale.format is deprecated.

- bpo-29851: importlib.reload() now raises ModuleNotFoundError if the module lacks a spec.

- bpo-28556: Various updates to typing module: typing.Counter, typing.ChainMap, improved ABC caching, etc. Original PRs by Jelle Zijlstra, Ivan Levkivskyi, Manuel Krebber, and Łukasz Langa.

- bpo-29100: Fix datetime.fromtimestamp() regression introduced in Python 3.6.0: check minimum and maximum years.

- bpo-29416: Prevent infinite loop in pathlib.Path.mkdir

- bpo-29444: Fixed out-of-bounds buffer access in the group() method of the match object. Based on patch by WGH.

- bpo-29377: Add WrapperDescriptorType, MethodWrapperType, and MethodDescriptorType built-in types to types module. Original patch by Manuel Krebber.

- bpo-29218: Unused install_misc command is now removed. It has been documented as unused since 2000. Patch by Eric N. Vander Weele.

- bpo-29368: The extend() method is now called instead of the append() method when unpickle collections.deque and other list-like objects. This can speed up unpickling to 2 times.

- bpo-29338: The help of a builtin or extension class now includes the constructor signature if __text_signature__ is provided for the class.

- bpo-29335: Fix subprocess.Popen.wait() when the child process has exited to a stopped instead of terminated state (ex: when under ptrace).

- bpo-29290: Fix a regression in argparse that help messages would wrap at non-breaking spaces.

- bpo-28735: Fixed the comparison of mock.MagickMock with mock.ANY.

- bpo-29197: Removed deprecated function ntpath.splitunc().

- bpo-29210: Removed support of deprecated argument “exclude” in tarfile.TarFile.add().

- bpo-29219: Fixed infinite recursion in the repr of uninitialized ctypes.CDLL instances.

- bpo-29192: Removed deprecated features in the http.cookies module.

- bpo-29193: A format string argument for string.Formatter.format() is now positional-only.

- bpo-29195: Removed support of deprecated undocumented keyword arguments in methods of regular expression objects.

- bpo-28969: Fixed race condition in C implementation of functools.lru_cache. KeyError could be raised when cached function with full cache was simultaneously called from differen threads with the same uncached arguments.

- bpo-20804: The unittest.mock.sentinel attributes now preserve their identity when they are copied or pickled.

- bpo-29142: In urllib.request, suffixes in no_proxy environment variable with leading dots could match related hostnames again (e.g. .b.c matches a.b.c). Patch by Milan Oberkirch.

- bpo-28961: Fix unittest.mock._Call helper: don’t ignore the name parameter anymore. Patch written by Jiajun Huang.

- bpo-15812: inspect.getframeinfo() now correctly shows the first line of a context. Patch by Sam Breese.

- bpo-28985: Update authorizer constants in sqlite3 module. Patch by Dingyuan Wang.

- bpo-29079: Prevent infinite loop in pathlib.resolve() on Windows

- bpo-13051: Fixed recursion errors in large or resized curses.textpad.Textbox. Based on patch by Tycho Andersen.

- bpo-9770: curses.ascii predicates now work correctly with negative integers.

- bpo-28427: old keys should not remove new values from WeakValueDictionary when collecting from another thread.

- bpo-28923: Remove editor artifacts from Tix.py.

- bpo-28871: Fixed a crash when deallocate deep ElementTree.

- bpo-19542: Fix bugs in WeakValueDictionary.setdefault() and WeakValueDictionary.pop() when a GC collection happens in another thread.

- bpo-20191: Fixed a crash in resource.prlimit() when passing a sequence that doesn’t own its elements as limits.

- bpo-16255: subprocess.Popen uses /system/bin/sh on Android as the shell, instead of /bin/sh.

- bpo-28779: multiprocessing.set_forkserver_preload() would crash the forkserver process if a preloaded module instantiated some multiprocessing objects such as locks.

- bpo-26937: The chown() method of the tarfile.TarFile class does not fail now when the grp module cannot be imported, as for example on Android platforms.

- bpo-28847: dbm.dumb now supports reading read-only files and no longer writes the index file when it is not changed. A deprecation warning is now emitted if the index file is missed and recreated in the ‘r’ and ‘w’ modes (will be an error in future Python releases).

- bpo-27030: Unknown escapes consisting of `'\'` and an ASCII letter in re.sub() replacement templates regular expressions now are errors.

- bpo-28835: Fix a regression introduced in warnings.catch_warnings(): call warnings.showwarning() if it was overridden inside the context manager.

- bpo-27172: To assist with upgrades from 2.7, the previously documented deprecation of `inspect.getfullargspec()` has been reversed. This decision may be revisited again after the Python 2.7 branch is no longer officially supported.

- bpo-28740: Add sys.getandroidapilevel(): return the build time API version of Android as an integer. Function only available on Android.

- bpo-26273: Add new `socket.TCP_CONGESTION` (Linux 2.6.13) and `socket.TCP_USER_TIMEOUT` (Linux 2.6.37) constants. Patch written by Omar Sandoval.

- bpo-28752: Restored the __reduce__() methods of datetime objects.

- bpo-28727: Regular expression patterns, _sre.SRE_Pattern objects created by re.compile(), become comparable (only x==y and x!=y operators). This change should fix the bpo-18383: don’t duplicate warning filters when the warnings module is reloaded (thing usually only done in unit tests).

- bpo-20572: Remove the subprocess.Popen.wait endtime parameter. It was deprecated in 3.4 and undocumented prior to that.

- bpo-25659: In ctypes, prevent a crash calling the from_buffer() and from_buffer_copy() methods on abstract classes like Array.

- bpo-28548: In the “http.server” module, parse the protocol version if possible, to avoid using HTTP 0.9 in some error responses.

- bpo-19717: Makes Path.resolve() succeed on paths that do not exist. Patch by Vajrasky Kok

- bpo-28563: Fixed possible DoS and arbitrary code execution when handle plural form selections in the gettext module. The expression parser now supports exact syntax supported by GNU gettext.

- bpo-28387: Fixed possible crash in _io.TextIOWrapper deallocator when the garbage collector is invoked in other thread. Based on patch by Sebastian Cufre.

- bpo-27517: LZMA compressor and decompressor no longer raise exceptions if given empty data twice. Patch by Benjamin Fogle.

- bpo-28549: Fixed segfault in curses’s addch() with ncurses6.

- bpo-28449: tarfile.open() with mode “r” or “r:” now tries to open a tar file with compression before trying to open it without compression. Otherwise it had 50% chance failed with ignore_zeros=True.

- bpo-23262: The webbrowser module now supports Firefox 36+ and derived browsers. Based on patch by Oleg Broytman.

- bpo-24241: The webbrowser in an X environment now prefers using the default browser directly. Also, the webbrowser register() function now has a documented ‘preferred’ argument, to specify browsers to be returned by get() with no arguments. Patch by David Steele

- bpo-27939: Fixed bugs in tkinter.ttk.LabeledScale and tkinter.Scale caused by representing the scale as float value internally in Tk. tkinter.IntVar now works if float value is set to underlying Tk variable.

- bpo-28255: calendar.TextCalendar.prweek() no longer prints a space after a weeks’s calendar. calendar.TextCalendar.pryear() no longer prints redundant newline after a year’s calendar. Based on patch by Xiang Zhang.

- bpo-28255: calendar.TextCalendar.prmonth() no longer prints a space at the start of new line after printing a month’s calendar. Patch by Xiang Zhang.

- bpo-20491: The textwrap.TextWrapper class now honors non-breaking spaces. Based on patch by Kaarle Ritvanen.

- bpo-28353: os.fwalk() no longer fails on broken links.

- bpo-28430: Fix iterator of C implemented asyncio.Future doesn’t accept non-None value is passed to it.send(val).

- bpo-27025: Generated names for Tkinter widgets now start by the “!” prefix for readability.

- bpo-25464: Fixed HList.header_exists() in tkinter.tix module by addin a workaround to Tix library bug.

- bpo-28488: shutil.make_archive() no longer adds entry “./” to ZIP archive.

- bpo-25953: re.sub() now raises an error for invalid numerical group reference in replacement template even if the pattern is not found in the string. Error message for invalid group reference now includes the group index and the position of the reference. Based on patch by SilentGhost.

- bpo-28469: timeit now uses the sequence 1, 2, 5, 10, 20, 50,… instead of 1, 10, 100,… for autoranging.

- bpo-28115: Command-line interface of the zipfile module now uses argparse. Added support of long options.

- bpo-18219: Optimize csv.DictWriter for large number of columns. Patch by Mariatta Wijaya.

- bpo-28448: Fix C implemented asyncio.Future didn’t work on Windows.

- bpo-23214: In the “io” module, the argument to BufferedReader and BytesIO’s read1() methods is now optional and can be -1, matching the BufferedIOBase specification.

- bpo-28480: Fix error building socket module when multithreading is disabled.

- bpo-28240: timeit: remove `-c/--clock` and `-t/--time` command line options which were deprecated since Python 3.3.

- bpo-28240: timeit now repeats the benchmarks 5 times instead of only 3 to make benchmarks more reliable.

- bpo-28240: timeit autorange now uses a single loop iteration if the benchmark takes less than 10 seconds, instead of 10 iterations. “python3 -m timeit -s ‘import time’ ‘time.sleep(1)’” now takes 4 seconds instead of 40 seconds.

- Distutils.sdist now looks for README and setup.py files with case sensitivity. This behavior matches that found in Setuptools 6.0 and later. See setuptools 100 for rationale.

- bpo-24452: Make webbrowser support Chrome on Mac OS X. Patch by Ned Batchelder.

- bpo-20766: Fix references leaked by pdb in the handling of SIGINT handlers.

- bpo-27998: Fixed bytes path support in os.scandir() on Windows. Patch by Eryk Sun.

- bpo-28317: The disassembler now decodes FORMAT_VALUE argument.

- bpo-28380: unittest.mock Mock autospec functions now properly support assert_called, assert_not_called, and assert_called_once.

- bpo-28229: lzma module now supports pathlib.

- bpo-28321: Fixed writing non-BMP characters with binary format in plistlib.

- bpo-28225: bz2 module now supports pathlib. Initial patch by Ethan Furman.

- bpo-28227: gzip now supports pathlib. Patch by Ethan Furman.

- bpo-28332: Deprecated silent truncations in socket.htons and socket.ntohs. Original patch by Oren Milman.

- bpo-27358: Optimized merging var-keyword arguments and improved error message when passing a non-mapping as a var-keyword argument.

- bpo-28257: Improved error message when passing a non-iterable as a var-positional argument. Added opcode BUILD_TUPLE_UNPACK_WITH_CALL.

- bpo-28322: Fixed possible crashes when unpickle itertools objects from incorrect pickle data. Based on patch by John Leitch.

- bpo-28228: imghdr now supports pathlib.

- bpo-28226: compileall now supports pathlib.

- bpo-28314: Fix function declaration (C flags) for the getiterator() method of xml.etree.ElementTree.Element.

- bpo-28148: Stop using localtime() and gmtime() in the time module.

  Introduced platform independent _PyTime_localtime API that is similar to POSIX localtime_r, but available on all platforms. Patch by Ed Schouten.

- bpo-28253: Fixed calendar functions for extreme months: 0001-01 and 9999-12.

  Methods itermonthdays() and itermonthdays2() are reimplemented so that they don’t call itermonthdates() which can cause datetime.date under/overflow.

- bpo-28275: Fixed possible use after free in the decompress() methods of the LZMADecompressor and BZ2Decompressor classes. Original patch by John Leitch.

- bpo-27897: Fixed possible crash in sqlite3.Connection.create_collation() if pass invalid string-like object as a name. Patch by Xiang Zhang.

- bpo-18844: random.choices() now has k as a keyword-only argument to improve the readability of common cases and come into line with the signature used in other languages.

- bpo-18893: Fix invalid exception handling in Lib/ctypes/macholib/dyld.py. Patch by Madison May.

- bpo-27611: Fixed support of default root window in the tkinter.tix module. Added the master parameter in the DisplayStyle constructor.

- bpo-27348: In the traceback module, restore the formatting of exception messages like “Exception: None”. This fixes a regression introduced in 3.5a2.

- bpo-25651: Allow falsy values to be used for msg parameter of subTest().

- bpo-27778: Fix a memory leak in os.getrandom() when the getrandom() is interrupted by a signal and a signal handler raises a Python exception.

- bpo-28200: Fix memory leak on Windows in the os module (fix path_converter() function).

- bpo-25400: RobotFileParser now correctly returns default values for crawl_delay and request_rate. Initial patch by Peter Wirtz.

- bpo-27932: Prevent memory leak in win32_ver().

- Fix UnboundLocalError in socket._sendfile_use_sendfile.

- bpo-28075: Check for ERROR_ACCESS_DENIED in Windows implementation of os.stat(). Patch by Eryk Sun.

- bpo-22493: Warning message emitted by using inline flags in the middle of regular expression now contains a (truncated) regex pattern. Patch by Tim Graham.

- bpo-25270: Prevent codecs.escape_encode() from raising SystemError when an empty bytestring is passed.

- bpo-28181: Get antigravity over HTTPS. Patch by Kaartic Sivaraam.

- bpo-25895: Enable WebSocket URL schemes in urllib.parse.urljoin. Patch by Gergely Imreh and Markus Holtermann.

- bpo-28114: Fix a crash in parse_envlist() when env contains byte strings. Patch by Eryk Sun.

- bpo-27599: Fixed buffer overrun in binascii.b2a_qp() and binascii.a2b_qp().

- bpo-27906: Fix socket accept exhaustion during high TCP traffic. Patch by Kevin Conway.

- bpo-28174: Handle when SO_REUSEPORT isn’t properly supported. Patch by Seth Michael Larson.

- bpo-26654: Inspect functools.partial in asyncio.Handle.__repr__. Patch by iceboy.

- bpo-26909: Fix slow pipes IO in asyncio. Patch by INADA Naoki.

- bpo-28176: Fix callbacks race in asyncio.SelectorLoop.sock_connect.

- bpo-27759: Fix selectors incorrectly retain invalid file descriptors. Patch by Mark Williams.

- bpo-28325: Remove vestigial MacOS 9 macurl2path module and its tests.

- bpo-28368: Refuse monitoring processes if the child watcher has no loop attached. Patch by Vincent Michel.

- bpo-28369: Raise RuntimeError when transport’s FD is used with add_reader, add_writer, etc.

- bpo-28370: Speedup asyncio.StreamReader.readexactly. Patch by Коренберг Марк.

- bpo-28371: Deprecate passing asyncio.Handles to run_in_executor.

- bpo-28372: Fix asyncio to support formatting of non-python coroutines.

- bpo-28399: Remove UNIX socket from FS before binding. Patch by Коренберг Марк.

- bpo-27972: Prohibit Tasks to await on themselves.

- bpo-24142: Reading a corrupt config file left configparser in an invalid state. Original patch by Florian Höch.

- bpo-29581: ABCMeta.__new__ now accepts `**kwargs`, allowing abstract base classes to use keyword parameters in __init_subclass__. Patch by Nate Soares.

- bpo-25532: inspect.unwrap() will now only try to unwrap an object sys.getrecursionlimit() times, to protect against objects which create a new object on every attribute access.

- bpo-30177: path.resolve(strict=False) no longer cuts the path after the first element not present in the filesystem. Patch by Antoine Pietri.

### Documentation

- bpo-31294: Fix incomplete code snippet in the ZeroMQSocketListener and ZeroMQSocketHandler examples and adapt them to Python 3.

- bpo-21649: Add RFC 7525 and Mozilla server side TLS links to SSL documentation.

- bpo-31128: Allow the pydoc server to bind to arbitrary hostnames.

- bpo-30803: Clarify doc on truth value testing. Original patch by Peter Thomassen.

- bpo-30176: Add missing attribute related constants in curses documentation.

- bpo-30052: the link targets for `bytes()` and `bytearray()` are now their respective type definitions, rather than the corresponding builtin function entries. Use bytes and bytearray to reference the latter.

  In order to ensure this and future cross-reference updates are applied automatically, the daily documentation builds now disable the default output caching features in Sphinx.

- bpo-26985: Add missing info of code object in inspect documentation.

- bpo-19824: Improve the documentation for, and links to, template strings by emphasizing their utility for internationalization, and by clarifying some usage constraints. (See also: bpo-20314, bpo-12518)

- bpo-28929: Link the documentation to its source file on GitHub.

- bpo-25008: Document smtpd.py as effectively deprecated and add a pointer to aiosmtpd, a third-party asyncio-based replacement.

- bpo-26355: Add canonical header link on each page to corresponding major version of the documentation. Patch by Matthias Bussonnier.

- bpo-29349: Fix Python 2 syntax in code for building the documentation.

- bpo-23722: The data model reference and the porting section in the 3.6 What’s New guide now cover the additional `__classcell__` handling needed for custom metaclasses to fully support PEP 487 and zero-argument `super()`.

- bpo-28513: Documented command-line interface of zipfile.

### Tests

- bpo-29639: test.support.HOST is now “localhost”, a new HOSTv4 constant has been added for your `127.0.0.1` needs, similar to the existing HOSTv6 constant.
- bpo-31320: Silence traceback in test_ssl
- bpo-31346: Prefer PROTOCOL_TLS_CLIENT and PROTOCOL_TLS_SERVER protocols for SSLContext.
- bpo-25674: Remove sha256.tbs-internet.com ssl test
- bpo-30715: Address ALPN callback changes for OpenSSL 1.1.0f. The latest version behaves like OpenSSL 1.0.2 and no longer aborts handshake.
- bpo-30822: regrtest: Exclude tzdata from regrtest –all. When running the test suite using –use=all / -u all, exclude tzdata since it makes test_datetime too slow (15-20 min on some buildbots) which then times out on some buildbots. Fix also regrtest command line parser to allow passing -u extralargefile to run test_zipfile64.
- bpo-30695: Add the `set_nomemory(start, stop)` and `remove_mem_hooks()` functions to the _testcapi module.
- bpo-30357: test_thread: setUp() now uses support.threading_setup() and support.threading_cleanup() to wait until threads complete to avoid random side effects on following tests. Initial patch written by Grzegorz Grzywacz.
- bpo-30197: Enhanced functions swap_attr() and swap_item() in the test.support module. They now work when delete replaced attribute or item inside the with statement. The old value of the attribute or item (or None if it doesn’t exist) now will be assigned to the target of the “as” clause, if there is one.
- bpo-24932: Use proper command line parsing in _testembed
- bpo-28950: Disallow -j0 to be combined with -T/-l in regrtest command line arguments.
- bpo-28683: Fix the tests that bind() a unix socket and raise PermissionError on Android for a non-root user.
- bpo-26936: Fix the test_socket failures on Android - getservbyname(), getservbyport() and getaddrinfo() are broken on some Android API levels.
- bpo-28666: Now test.support.rmtree is able to remove unwritable or unreadable directories.
- bpo-23839: Various caches now are cleared before running every test file.
- bpo-26944: Fix test_posix for Android where ‘id -G’ is entirely wrong or missing the effective gid.
- bpo-28409: regrtest: fix the parser of command line arguments.
- bpo-28217: Adds _testconsole module to test console input.
- bpo-26939: Add the support.setswitchinterval() function to fix test_functools hanging on the Android armv7 qemu emulator.

### Build

- bpo-31354: Allow –with-lto to be used on all builds, not just `make profile-opt`.

- bpo-31370: Remove support for building –without-threads.

  This option is not really useful anymore in the 21st century. Removing lots of conditional paths allows us to simplify the code base, including in difficult to maintain low-level internal code.

- bpo-31341: Per PEP 11, support for the IRIX operating system was removed.

- bpo-30854: Fix compile error when compiling –without-threads. Patch by Masayuki Yamamoto.

- bpo-30687: Locate msbuild.exe on Windows when building rather than vcvarsall.bat

- bpo-20210: Support the disabled marker in Setup files. Extension modules listed after this marker are not built at all, neither by the Makefile nor by setup.py.

- bpo-29941: Add `--with-assertions` configure flag to explicitly enable C `assert()` checks. Defaults to off. `--with-pydebug` implies `--with-assertions`.

- bpo-28787: Fix out-of-tree builds of Python when configured with `--with--dtrace`.

- bpo-29243: Prevent unnecessary rebuilding of Python during `make test`, `make install` and some other make targets when configured with `--enable-optimizations`.

- bpo-23404: Don’t regenerate generated files based on file modification time anymore: the action is now explicit. Replace `make touch` with `make regen-all`.

- bpo-29643: Fix `--enable-optimization` didn’t work.

- bpo-27593: sys.version and the platform module python_build(), python_branch(), and python_revision() functions now use git information rather than hg when building from a repo.

- bpo-29572: Update Windows build and OS X installers to use OpenSSL 1.0.2k.

- bpo-27659: Prohibit implicit C function declarations: use `-Werror=implicit-function-declaration` when possible (GCC and Clang, but it depends on the compiler version). Patch written by Chi Hsuan Yen.

- bpo-29384: Remove old Be OS helper scripts.

- bpo-26851: Set Android compilation and link flags.

- bpo-28768: Fix implicit declaration of function _setmode. Patch by Masayuki Yamamoto

- bpo-29080: Removes hard dependency on hg.exe from PCBuild/build.bat

- bpo-23903: Added missed names to PC/python3.def.

- bpo-28762: lockf() is available on Android API level 24, but the F_LOCK macro is not defined in android-ndk-r13.

- bpo-28538: Fix the compilation error that occurs because if_nameindex() is available on Android API level 24, but the if_nameindex structure is not defined.

- bpo-20211: Do not add the directory for installing C header files and the directory for installing object code libraries to the cross compilation search paths. Original patch by Thomas Petazzoni.

- bpo-28849: Do not define sys.implementation._multiarch on Android.

- bpo-10656: Fix out-of-tree building on AIX. Patch by Tristan Carel and Michael Haubenwallner.

- bpo-26359: Rename –with-optimiations to –enable-optimizations.

- bpo-28444: Fix missing extensions modules when cross compiling.

- bpo-28208: Update Windows build and OS X installers to use SQLite 3.14.2.

- bpo-28248: Update Windows build and OS X installers to use OpenSSL 1.0.2j.

- bpo-21124: Fix building the _struct module on Cygwin by passing `NULL` instead of `&PyType_Type` to PyVarObject_HEAD_INIT. Patch by Masayuki Yamamoto.

- bpo-13756: Fix building extensions modules on Cygwin. Patch by Roumen Petrov, based on original patch by Jason Tishler.

- bpo-21085: Add configure check for siginfo_t.si_band, which Cygwin does not provide. Patch by Masayuki Yamamoto with review and rebase by Erik Bray.

- bpo-28258: Fixed build with Estonian locale (python-config and distclean targets in Makefile). Patch by Arfrever Frehtes Taifersar Arahesis.

- bpo-26661: setup.py now detects system libffi with multiarch wrapper.

- bpo-27979: A full copy of libffi is no longer bundled for use when building _ctypes on non-OSX UNIX platforms. An installed copy of libffi is now required when building _ctypes on such platforms.

- bpo-15819: Remove redundant include search directory option for building outside the source tree.

- bpo-28676: Prevent missing ‘getentropy’ declaration warning on macOS. Patch by Gareth Rees.

### Windows

- bpo-31392: Update Windows build to use OpenSSL 1.1.0f
- bpo-30389: Adds detection of Visual Studio 2017 to distutils on Windows.
- bpo-31358: zlib is no longer bundled in the CPython source, instead it is downloaded on demand just like bz2, lzma, OpenSSL, Tcl/Tk, and SQLite.
- bpo-31340: Change to building with MSVC v141 (included with Visual Studio 2017)
- bpo-30581: os.cpu_count() now returns the correct number of processors on Windows when the number of logical processors is greater than 64.
- bpo-30916: Pre-build OpenSSL, Tcl and Tk and include the binaries in the build.
- bpo-30731: Add a missing xmlns to python.manifest so that it matches the schema.
- bpo-30291: Allow requiring 64-bit interpreters from py.exe using -64 suffix. Contributed by Steve (Gadget) Barnes.
- bpo-30362: Adds list options (-0, -0p) to py.exe launcher. Contributed by Steve Barnes.
- bpo-23451: Fix socket deprecation warnings in socketmodule.c. Patch by Segev Finer.
- bpo-30450: The build process on Windows no longer depends on Subversion, instead pulling external code from GitHub via a Python script. If Python 3.6 is not found on the system (via `py -3.6`), NuGet is used to download a copy of 32-bit Python.
- bpo-29579: Removes readme.txt from the installer.
- bpo-25778: winreg does not truncate string correctly (Patch by Eryk Sun)
- bpo-28896: Deprecate WindowsRegistryFinder and disable it by default
- bpo-28522: Fixes mishandled buffer reallocation in getpathp.c
- bpo-28402: Adds signed catalog files for stdlib on Windows.
- bpo-28333: Enables Unicode for ps1/ps2 and input() prompts. (Patch by Eryk Sun)
- bpo-28251: Improvements to help manuals on Windows.
- bpo-28110: launcher.msi has different product codes between 32-bit and 64-bit
- bpo-28161: Opening CON for write access fails
- bpo-28162: WindowsConsoleIO readall() fails if first line starts with Ctrl+Z
- bpo-28163: WindowsConsoleIO fileno() passes wrong flags to _open_osfhandle
- bpo-28164: _PyIO_get_console_type fails for various paths
- bpo-28137: Renames Windows path file to ._pth
- bpo-28138: Windows ._pth file should allow import site

### IDLE

- bpo-31493: IDLE code context – fix code update and font update timers.

  Canceling timers prevents a warning message when test_idle completes.

- bpo-31488: IDLE - Update non-key options in former extension classes. When applying configdialog changes, call .reload for each feature class. Change ParenMatch so updated options affect existing instances attached to existing editor windows.

- bpo-31477: IDLE - Improve rstrip entry in doc. Strip trailing whitespace strips more than blank spaces. Multiline string literals are not skipped.

- bpo-31480: IDLE - make tests pass with zzdummy extension disabled by default.

- bpo-31421: Document how IDLE runs tkinter programs. IDLE calls tcl/tk update in the background in order to make live

  interaction and experimentation with tkinter applications much easier.

- bpo-31414: IDLE – fix tk entry box tests by deleting first. Adding to an int entry is not the same as deleting and inserting because int(‘’) will fail.

- bpo-31051: Rearrange IDLE configdialog GenPage into Window, Editor, and Help sections.

- bpo-30617: IDLE - Add docstrings and tests for outwin subclass of editor.

  Move some data and functions from the class to module level. Patch by Cheryl Sabella.

- bpo-31287: IDLE - Do not modify tkinter.message in test_configdialog.

- bpo-27099: Convert IDLE’s built-in ‘extensions’ to regular features.

  About 10 IDLE features were implemented as supposedly optional extensions. Their different behavior could be confusing or worse for users and not good for maintenance. Hence the conversion.

  The main difference for users is that user configurable key bindings for builtin features are now handled uniformly. Now, editing a binding in a keyset only affects its value in the keyset. All bindings are defined together in the system-specific default keysets in config-extensions.def. All custom keysets are saved as a whole in config-extension.cfg. All take effect as soon as one clicks Apply or Ok.

  The affected events are ‘<<force-open-completions>>’, ‘<<expand-word>>’, ‘<<force-open-calltip>>’, ‘<<flash-paren>>’, ‘<<format-paragraph>>’, ‘<<run-module>>’, ‘<<check-module>>’, and ‘<<zoom-height>>’. Any (global) customizations made before 3.6.3 will not affect their keyset-specific customization after 3.6.3. and vice versa.

  Initial patch by Charles Wohlganger.

- bpo-31206: IDLE: Factor HighPage(Frame) class from ConfigDialog. Patch by Cheryl Sabella.

- bpo-31001: Add tests for configdialog highlight tab. Patch by Cheryl Sabella.

- bpo-31205: IDLE: Factor KeysPage(Frame) class from ConfigDialog. The slightly modified tests continue to pass. Patch by Cheryl Sabella.

- bpo-31130: IDLE – stop leaks in test_configdialog. Initial patch by Victor Stinner.

- bpo-31002: Add tests for configdialog keys tab. Patch by Cheryl Sabella.

- bpo-19903: IDLE: Calltips use `inspect.signature` instead of `inspect.getfullargspec`. This improves calltips for builtins converted to use Argument Clinic. Patch by Louie Lu.

- bpo-31083: IDLE - Add an outline of a TabPage class in configdialog. Update existing classes to match outline. Initial patch by Cheryl Sabella.

- bpo-31050: Factor GenPage(Frame) class from ConfigDialog. The slightly modified tests continue to pass. Patch by Cheryl Sabella.

- bpo-31004: IDLE - Factor FontPage(Frame) class from ConfigDialog.

  Slightly modified tests continue to pass. Fix General tests. Patch mostly by Cheryl Sabella.

- bpo-30781: IDLE - Use ttk widgets in ConfigDialog. Patches by Terry Jan Reedy and Cheryl Sabella.

- bpo-31060: IDLE - Finish rearranging methods of ConfigDialog Grouping methods pertaining to each tab and the buttons will aid writing tests and improving the tabs and will enable splitting the groups into classes.

- bpo-30853: IDLE – Factor a VarTrace class out of ConfigDialog.

  Instance tracers manages pairs consisting of a tk variable and a callback function. When tracing is turned on, setting the variable calls the function. Test coverage for the new class is 100%.

- bpo-31003: IDLE: Add more tests for General tab.

- bpo-30993: IDLE - Improve configdialog font page and tests.

  In configdialog: Document causal pathways in create_font_tab docstring. Simplify some attribute names. Move set_samples calls to var_changed_font (idea from Cheryl Sabella). Move related functions to positions after the create widgets function.

  In test_configdialog: Fix test_font_set so not order dependent. Fix renamed test_indent_scale so it tests the widget. Adjust tests for movement of set_samples call. Add tests for load functions. Put all font tests in one class and tab indent tests in another. Except for two lines, these tests completely cover the related functions.

- bpo-30981: IDLE – Add more configdialog font page tests.

- bpo-28523: IDLE: replace ‘colour’ with ‘color’ in configdialog.

- bpo-30917: Add tests for idlelib.config.IdleConf. Increase coverage from 46% to 96%. Patch by Louie Lu.

- bpo-30934: Document coverage details for idlelib tests.

  - Add section to idlelib/idle-test/README.txt.
  - Include check that branches are taken both ways.
  - Exclude IDLE-specific code that does not run during unit tests.

- bpo-30913: IDLE: Document ConfigDialog tk Vars, methods, and widgets in docstrings This will facilitate improving the dialog and splitting up the class. Original patch by Cheryl Sabella.

- bpo-30899: IDLE: Add tests for ConfigParser subclasses in config. Patch by Louie Lu.

- bpo-30881: IDLE: Add docstrings to browser.py. Patch by Cheryl Sabella.

- bpo-30851: IDLE: Remove unused variables in configdialog. One is a duplicate, one is set but cannot be altered by users. Patch by Cheryl Sabella.

- bpo-30870: IDLE: In Settings dialog, select font with Up, Down keys as well as mouse. Initial patch by Louie Lu.

- bpo-8231: IDLE: call config.IdleConf.GetUserCfgDir only once.

- bpo-30779: IDLE: Factor ConfigChanges class from configdialog, put in config; test. * In config, put dump test code in a function; run it and unittest in ‘if __name__ == ‘__main__’. * Add class config.ConfigChanges based on changes_class_v4.py on bpo issue. * Add class test_config.ChangesTest, partly using configdialog_tests_v1.py. * Revise configdialog to use ConfigChanges; see tracker msg297804. * Revise test_configdialog to match configdialog changes. * Remove configdialog functions unused or moved to ConfigChanges. Cheryl Sabella contributed parts of the patch.

- bpo-30777: IDLE: configdialog - Add docstrings and fix comments. Patch by Cheryl Sabella.

- bpo-30495: IDLE: Improve textview with docstrings, PEP8 names, and more tests. Patch by Cheryl Sabella.

- bpo-30723: IDLE: Make several improvements to parenmatch. Add ‘parens’ style to highlight both opener and closer. Make ‘default’ style, which is not default, a synonym for ‘opener’. Make time-delay work the same with all styles. Add help for config dialog extensions tab, including help for parenmatch. Add new tests. Original patch by Charles Wohlganger.

- bpo-30674: IDLE: add docstrings to grep module. Patch by Cheryl Sabella

- bpo-21519: IDLE’s basic custom key entry dialog now detects duplicates properly. Original patch by Saimadhav Heblikar.

- bpo-29910: IDLE no longer deletes a character after commenting out a region by a key shortcut. Add `return 'break'` for this and other potential conflicts between IDLE and default key bindings.

- bpo-30728: Review and change idlelib.configdialog names. Lowercase method and attribute names. Replace ‘colour’ with ‘color’, expand overly cryptic names, delete unneeded underscores. Replace `import *` with specific imports. Patches by Cheryl Sabella.

- bpo-6739: IDLE: Verify user-entered key sequences by trying to bind them with tk. Add tests for all 3 validation functions. Original patch by G Polo. Tests added by Cheryl Sabella.

- bpo-15786: Fix several problems with IDLE’s autocompletion box. The following should now work: clicking on selection box items; using the scrollbar; selecting an item by hitting Return. Hangs on MacOSX should no longer happen. Patch by Louie Lu.

- bpo-25514: Add doc subsubsection about IDLE failure to start. Popup no-connection message directs users to this section.

- bpo-30642: Fix reference leaks in IDLE tests. Patches by Louie Lu and Terry Jan Reedy.

- bpo-30495: Add docstrings for textview.py and use PEP8 names. Patches by Cheryl Sabella and Terry Jan Reedy.

- bpo-30290: Help-about: use pep8 names and add tests. Increase coverage to 100%. Patches by Louie Lu, Cheryl Sabella, and Terry Jan Reedy.

- bpo-30303: Add _utest option to textview; add new tests. Increase coverage to 100%. Patches by Louie Lu and Terry Jan Reedy.

- bpo-29071: IDLE colors f-string prefixes (but not invalid ur prefixes).

- bpo-28572: Add 10% to coverage of IDLE’s test_configdialog. Update and augment description of the configuration system.

### Tools/Demos

- bpo-30983: gdb integration commands (py-bt, etc.) work on optimized shared builds now, too. PEP 523 introduced _PyEval_EvalFrameDefault which inlines PyEval_EvalFrameEx on non-debug shared builds. This broke the ability to use py-bt, py-up, and a few other Python-specific gdb integrations. The problem is fixed by only looking for _PyEval_EvalFrameDefault frames in python-gdb.py. Original patch by Bruno “Polaco” Penteado.
- bpo-29748: Added the slice index converter in Argument Clinic.
- bpo-24037: Argument Clinic now uses the converter `bool(accept={int})` rather than `int` for semantical booleans. This avoids repeating the default value for Python and C and will help in converting to `bool` in future.
- bpo-29367: python-gdb.py now supports also `method-wrapper` (`wrapperobject`) objects.
- bpo-28023: Fix python-gdb.py didn’t support new dict implementation.
- bpo-15369: The pybench and pystone microbenchmark have been removed from Tools. Please use the new Python benchmark suite https://github.com/python/performance which is more reliable and includes a portable version of pybench working on Python 2 and Python 3.
- bpo-28102: The zipfile module CLI now prints usage to stderr. Patch by Stephen J. Turnbull.

### C API

- bpo-31338: Added the `Py_UNREACHABLE()` macro for code paths which are never expected to be reached. This and a few other useful macros are now documented in the C API manual.

- bpo-30832: Remove own implementation for thread-local storage.

  CPython has provided the own implementation for thread-local storage (TLS) on Python/thread.c, it’s used in the case which a platform has not supplied native TLS. However, currently all supported platforms (Windows and pthreads) have provided native TLS and defined the Py_HAVE_NATIVE_TLS macro with unconditional in any case.

- bpo-30708: PyUnicode_AsWideCharString() now raises a ValueError if the second argument is NULL and the wchar_t* string contains null characters.

- bpo-16500: Deprecate PyOS_AfterFork() and add PyOS_BeforeFork(), PyOS_AfterFork_Parent() and PyOS_AfterFork_Child().

- bpo-6532: The type of results of PyThread_start_new_thread() and PyThread_get_thread_ident(), and the id parameter of PyThreadState_SetAsyncExc() changed from “long” to “unsigned long”.

- bpo-27867: Function PySlice_GetIndicesEx() is deprecated and replaced with a macro if Py_LIMITED_API is not set or set to the value between 0x03050400 and 0x03060000 (not including) or 0x03060100 or higher. Added functions PySlice_Unpack() and PySlice_AdjustIndices().

- bpo-29083: Fixed the declaration of some public API functions. PyArg_VaParse() and PyArg_VaParseTupleAndKeywords() were not available in limited API. PyArg_ValidateKeywordArguments(), PyArg_UnpackTuple() and Py_BuildValue() were not available in limited API of version < 3.3 when PY_SSIZE_T_CLEAN is defined.

- bpo-28769: The result of PyUnicode_AsUTF8AndSize() and PyUnicode_AsUTF8() is now of type `const char *` rather of `char *`.

- bpo-29058: All stable API extensions added after Python 3.2 are now available only when Py_LIMITED_API is set to the PY_VERSION_HEX value of the minimum Python version supporting this API.

- bpo-28822: The index parameters start and end of PyUnicode_FindChar() are now adjusted to behave like `str[start:end]`.

- bpo-28808: PyUnicode_CompareWithASCIIString() now never raises exceptions.

- bpo-28761: The fields name and doc of structures PyMemberDef, PyGetSetDef, PyStructSequence_Field, PyStructSequence_Desc, and wrapperbase are now of type `const char *` rather of `char *`.

- bpo-28748: Private variable _Py_PackageContext is now of type `const char *` rather of `char *`.

- bpo-19569: Compiler warnings are now emitted if use most of deprecated functions.

- bpo-28426: Deprecated undocumented functions PyUnicode_AsEncodedObject(), PyUnicode_AsDecodedObject(), PyUnicode_AsDecodedUnicode() and PyUnicode_AsEncodedUnicode().

## Python 3.6.6 final

Release date: 2018-06-27

There were no new changes in version 3.6.6.

## Python 3.6.6 release candidate 1

Release date: 2018-06-11

### Core and Builtins

- bpo-33786: Fix asynchronous generators to handle GeneratorExit in athrow() correctly
- bpo-30654: Fixed reset of the SIGINT handler to SIG_DFL on interpreter shutdown even when there was a custom handler set previously. Patch by Philipp Kerling.
- bpo-33622: Fixed a leak when the garbage collector fails to add an object with the `__del__` method or referenced by it into the `gc.garbage` list. `PyGC_Collect()` can now be called when an exception is set and preserves it.
- bpo-31849: Fix signed/unsigned comparison warning in pyhash.c.
- bpo-33391: Fix a leak in set_symmetric_difference().
- bpo-28055: Fix unaligned accesses in siphash24(). Patch by Rolf Eike Beer.
- bpo-33231: Fix potential memory leak in `normalizestring()`.
- bpo-29922: Improved error messages in ‘async with’ when `__aenter__()` or `__aexit__()` return non-awaitable object.
- bpo-33199: Fix `ma_version_tag` in dict implementation is uninitialized when copying from key-sharing dict.
- bpo-33041: Fixed jumping when the function contains an `async for` loop.
- bpo-32282: Fix an unnecessary ifdef in the include of VersionHelpers.h in socketmodule on Windows.
- bpo-21983: Fix a crash in `ctypes.cast()` in case the type argument is a ctypes structured data type. Patch by Eryk Sun and Oren Milman.

### Library

- bpo-30167: Prevent site.main() exception if PYTHONSTARTUP is set. Patch by Steve Weber.
- bpo-33812: Datetime instance d with non-None tzinfo, but with d.tzinfo.utcoffset(d) returning None is now treated as naive by the astimezone() method.
- bpo-30805: Avoid race condition with debug logging
- bpo-33767: The concatenation (`+`) and repetition (`*`) sequence operations now raise `TypeError` instead of `SystemError` when performed on `mmap.mmap` objects. Patch by Zackery Spytz.
- bpo-32684: Fix gather to propagate cancellation of itself even with return_exceptions.
- bpo-33674: Fix a race condition in SSLProtocol.connection_made() of asyncio.sslproto: start immediately the handshake instead of using call_soon(). Previously, data_received() could be called before the handshake started, causing the handshake to hang or fail.
- bpo-31647: Fixed bug where calling write_eof() on a _SelectorSocketTransport after it’s already closed raises AttributeError.
- bpo-33672: Fix Task.__repr__ crash with Cython’s bogus coroutines
- bpo-33469: Fix RuntimeError after closing loop that used run_in_executor
- bpo-11874: Use a better regex when breaking usage into wrappable parts. Avoids bogus assertion errors from custom metavar strings.
- bpo-30877: Fixed a bug in the Python implementation of the JSON decoder that prevented the cache of parsed strings from clearing after finishing the decoding. Based on patch by c-fos.
- bpo-33548: tempfile._candidate_tempdir_list should consider common TEMP locations
- bpo-33542: Prevent `uuid.get_node` from using a DUID instead of a MAC on Windows. Patch by Zvi Effron
- bpo-26819: Fix race condition with `ReadTransport.resume_reading` in Windows proactor event loop.
- bpo-28556: Minor fixes in typing module: add annotations to `NamedTuple.__new__`, pass `*args` and `**kwds` in `Generic.__new__`. Original PRs by Paulius Šarka and Chad Dombrova.
- bpo-20087: Updated alias mapping with glibc 2.27 supported locales.
- bpo-33422: Fix trailing quotation marks getting deleted when looking up byte/string literals on pydoc. Patch by Andrés Delfino.
- bpo-33197: Update error message when constructing invalid inspect.Parameters Patch by Dong-hee Na.
- bpo-33383: Fixed crash in the get() method of the `dbm.ndbm` database object when it is called with a single argument.
- bpo-33329: Fix multiprocessing regression on newer glibcs
- bpo-991266: Fix quoting of the `Comment` attribute of `http.cookies.SimpleCookie`.
- bpo-33131: Upgrade bundled version of pip to 10.0.1.
- bpo-33308: Fixed a crash in the `parser` module when converting an ST object to a tree of tuples or lists with `line_info=False` and `col_info=True`.
- bpo-33263: Fix FD leak in `_SelectorSocketTransport` Patch by Vlad Starostin.
- bpo-33256: Fix display of `<module>` call in the html produced by `cgitb.html()`. Patch by Stéphane Blondon.
- bpo-33203: `random.Random.choice()` now raises `IndexError` for empty sequences consistently even when called from subclasses without a `getrandbits()` implementation.
- bpo-33224: Update difflib.mdiff() for PEP 479. Convert an uncaught StopIteration in a generator into a return-statement.
- bpo-33209: End framing at the end of C implementation of `pickle.Pickler.dump()`.
- bpo-32861: The urllib.robotparser’s `__str__` representation now includes wildcard entries and the “Crawl-delay” and “Request-rate” fields. Patch by Michael Lazar.
- bpo-33096: Allow ttk.Treeview.insert to insert iid that has a false boolean value. Note iid=0 and iid=False would be same. Patch by Garvit Khatri.
- bpo-33127: The ssl module now compiles with LibreSSL 2.7.1.
- bpo-33021: Release the GIL during fstat() calls, avoiding hang of all threads when calling mmap.mmap(), os.urandom(), and random.seed(). Patch by Nir Soffer.
- bpo-27683: Fix a regression in `ipaddress` that result of `hosts()` is empty when the network is constructed by a tuple containing an integer mask and only 1 bit left for addresses.
- bpo-32844: Fix wrong redirection of a low descriptor (0 or 1) to stderr in subprocess if another low descriptor is closed.
- bpo-31908: Fix output of cover files for `trace` module command-line tool. Previously emitted cover files only when `--missing` option was used. Patch by Michael Selik.
- bpo-31457: If nested log adapters are used, the inner `process()` methods are no longer omitted.
- bpo-16865: Support arrays >=2GiB in `ctypes`. Patch by Segev Finer.
- bpo-31238: pydoc: the stop() method of the private ServerThread class now waits until DocServer.serve_until_quit() completes and then explicitly sets its docserver attribute to None to break a reference cycle.

### Documentation

- bpo-33503: Fix broken pypi link
- bpo-33421: Add missing documentation for `typing.AsyncContextManager`.
- bpo-33378: Add Korean language switcher for https://docs.python.org/3/
- bpo-33276: Clarify that the `__path__` attribute on modules cannot be just any value.
- bpo-33201: Modernize documentation for writing C extension types.
- bpo-33195: Deprecate `Py_UNICODE` usage in `c-api/arg` document. `Py_UNICODE` related APIs are deprecated since Python 3.3, but it is missed in the document.
- bpo-33126: Document PyBuffer_ToContiguous().
- bpo-27212: Modify documentation for the `islice()` recipe to consume initial values up to the start index.
- bpo-28247: Update `zipapp` documentation to describe how to make standalone applications.
- bpo-18802: Documentation changes for ipaddress. Patch by Jon Foster and Berker Peksag.
- bpo-27428: Update documentation to clarify that `WindowsRegistryFinder` implements `MetaPathFinder`. (Patch by Himanshu Lakhara)
- bpo-8243: Add a note about curses.addch and curses.addstr exception behavior when writing outside a window, or pad.
- bpo-31432: Clarify meaning of CERT_NONE, CERT_OPTIONAL, and CERT_REQUIRED flags for ssl.SSLContext.verify_mode.

### Tests

- bpo-33655: Ignore test_posix_fallocate failures on BSD platforms that might be due to running on ZFS.
- bpo-19417: Add test_bdb.py.

### Build

- bpo-5755: Move `-Wstrict-prototypes` option to `CFLAGS_NODIST` from `OPT`. This option emitted annoying warnings when building extension modules written in C++.
- bpo-33614: Ensures module definition files for the stable ABI on Windows are correctly regenerated.
- bpo-33522: Enable CI builds on Visual Studio Team Services at https://python.visualstudio.com/cpython
- bpo-33012: Add `-Wno-cast-function-type` for gcc 8 for silencing warnings about function casts like casting to PyCFunction in method definition lists.
- bpo-33394: Enable the verbose build for extension modules, when GNU make is passed macros on the command line.

### Windows

- bpo-33184: Update Windows installer to OpenSSL 1.0.2o.

### macOS

- bpo-33184: Update macOS installer build to use OpenSSL 1.0.2o.

### IDLE

- bpo-33656: On Windows, add API call saying that tk scales for DPI. On Windows 8.1+ or 10, with DPI compatibility properties of the Python binary unchanged, and a monitor resolution greater than 96 DPI, this should make text and lines sharper. It should otherwise have no effect.
- bpo-33768: Clicking on a context line moves that line to the top of the editor window.
- bpo-33763: IDLE: Use read-only text widget for code context instead of label widget.
- bpo-33664: Scroll IDLE editor text by lines. Previously, the mouse wheel and scrollbar slider moved text by a fixed number of pixels, resulting in partial lines at the top of the editor box. The change also applies to the shell and grep output windows, but not to read-only text views.
- bpo-33679: Enable theme-specific color configuration for Code Context. Use the Highlights tab to see the setting for built-in themes or add settings to custom themes.
- bpo-33642: Display up to maxlines non-blank lines for Code Context. If there is no current context, show a single blank line.
- bpo-33628: IDLE: Cleanup codecontext.py and its test.
- bpo-33564: IDLE’s code context now recognizes async as a block opener.
- bpo-29706: IDLE now colors async and await as keywords in 3.6. They become full keywords in 3.7.
- bpo-21474: Update word/identifier definition from ascii to unicode. In text and entry boxes, this affects selection by double-click, movement left/right by control-left/right, and deletion left/right by control-BACKSPACE/DEL.
- bpo-33204: IDLE: consistently color invalid string prefixes. A ‘u’ string prefix cannot be paired with either ‘r’ or ‘f’. Consistently color as much of the prefix, starting at the right, as is valid. Revise and extend colorizer test.
- bpo-32831: Add docstrings and tests for codecontext.

### Tools/Demos

- bpo-33189: pygettext.py now recognizes only literal strings as docstrings and translatable strings, and rejects bytes literals and f-string expressions.
- bpo-31920: Fixed handling directories as arguments in the `pygettext` script. Based on patch by Oleg Krasnikov.
- bpo-29673: Fix pystackv and pystack gdbinit macros.
- bpo-32885: Add an `-n` flag for `Tools/scripts/pathfix.py` to disable automatic backup creation (files with `~` suffix).
- bpo-31583: Fix 2to3 for using with –add-suffix option but without –output-dir option for relative path to files in current directory.

### C API

- bpo-32374: Document that m_traverse for multi-phase initialized modules can be called with m_state=NULL, and add a sanity check

## Python 3.6.5 final

Release date: 2018-03-28

### Tests

- bpo-32872: Avoid regrtest compatibility issue with namespace packages.

### Build

- bpo-33163: Upgrade pip to 9.0.3 and setuptools to v39.0.1.

## Python 3.6.5 release candidate 1

Release date: 2018-03-13

### Security

- bpo-33001: Minimal fix to prevent buffer overrun in os.symlink on Windows
- bpo-32981: Regexes in difflib and poplib were vulnerable to catastrophic backtracking. These regexes formed potential DOS vectors (REDOS). They have been refactored. This resolves CVE-2018-1060 and CVE-2018-1061. Patch by Jamie Davis.

### Core and Builtins

- bpo-33026: Fixed jumping out of “with” block by setting f_lineno.
- bpo-17288: Prevent jumps from ‘return’ and ‘exception’ trace events.
- bpo-32889: Update Valgrind suppression list to account for the rename of `Py_ADDRESS_IN_RANG` to `address_in_range`.
- bpo-32650: Pdb and other debuggers dependent on bdb.py will correctly step over (next command) native coroutines. Patch by Pablo Galindo.
- bpo-32685: Improve suggestion when the Python 2 form of print statement is either present on the same line as the header of a compound statement or else terminated by a semi-colon instead of a newline. Patch by Nitish Chandra.
- bpo-32583: Fix possible crashing in builtin Unicode decoders caused by write out-of-bound errors when using customized decode error handlers.
- bpo-26163: Improved frozenset() hash to create more distinct hash values when faced with datasets containing many similar values.
- bpo-27169: The `__debug__` constant is now optimized out at compile time. This fixes also bpo-22091.
- bpo-32329: `sys.flags.hash_randomization` is now properly set to 0 when hash randomization is turned off by `PYTHONHASHSEED=0`.
- bpo-30416: The optimizer is now protected from spending much time doing complex calculations and consuming much memory for creating large constants in constant folding.
- bpo-18533: `repr()` on a dict containing its own `values()` or `items()` no longer raises `RecursionError`; OrderedDict similarly. Instead, use `...`, as for other recursive structures. Patch by Ben North.
- bpo-32028: Leading whitespace is now correctly ignored when generating suggestions for converting Py2 print statements to Py3 builtin print function calls. Patch by Sanyam Khurana.
- bpo-32137: The repr of deeply nested dict now raises a RecursionError instead of crashing due to a stack overflow.

### Library

- bpo-33064: lib2to3 now properly supports trailing commas after `*args` and `**kwargs` in function signatures.

- bpo-31804: Avoid failing in multiprocessing.Process if the standard streams are closed or None at exit.

- bpo-33037: Skip sending/receiving data after SSL transport closing.

- bpo-30353: Fix ctypes pass-by-value for structs on 64-bit Cygwin/MinGW.

- bpo-33009: Fix inspect.signature() for single-parameter partialmethods.

- bpo-32969: Expose several missing constants in zlib and fix corresponding documentation.

- bpo-32713: Fixed tarfile.itn handling of out-of-bounds float values. Patch by Joffrey Fuhrer.

- bpo-30622: The ssl module now detects missing NPN support in LibreSSL.

- bpo-32922: dbm.open() now encodes filename with the filesystem encoding rather than default encoding.

- bpo-32859: In `os.dup2`, don’t check every call whether the `dup3` syscall exists or not.

- bpo-21060: Rewrite confusing message from setup.py upload from “No dist file created in earlier command” to the more helpful “Must create and upload files in one command”.

- bpo-32857: In `tkinter`, `after_cancel(None)` now raises a `ValueError` instead of canceling the first scheduled function. Patch by Cheryl Sabella.

- bpo-32852: Make sure sys.argv remains as a list when running trace.

- bpo-32841: Fixed `asyncio.Condition` issue which silently ignored cancellation after notifying and cancelling a conditional lock. Patch by Bar Harel.

- bpo-31787: Fixed refleaks of `__init__()` methods in various modules. (Contributed by Oren Milman)

- bpo-30157: Fixed guessing quote and delimiter in csv.Sniffer.sniff() when only the last field is quoted. Patch by Jake Davis.

- bpo-32394: socket: Remove TCP_FASTOPEN, TCP_KEEPCNT flags on older version Windows during run-time.

- bpo-32777: Fix a rare but potential pre-exec child process deadlock in subprocess on POSIX systems when marking file descriptors inheritable on exec in the child process. This bug appears to have been introduced in 3.4.

- bpo-32647: The ctypes module used to depend on indirect linking for dlopen. The shared extension is now explicitly linked against libdl on platforms with dl.

- bpo-32734: Fixed `asyncio.Lock()` safety issue which allowed acquiring and locking the same lock multiple times, without it being free. Patch by Bar Harel.

- bpo-32727: Do not include name field in SMTP envelope from address. Patch by Stéphane Wirtel

- bpo-27931: Fix email address header parsing error when the username is an empty quoted string. Patch by Xiang Zhang.

- bpo-32304: distutils’ upload command no longer corrupts tar files ending with a CR byte, and no longer tries to convert CR to CRLF in any of the upload text fields.

- bpo-32502: uuid.uuid1 no longer raises an exception if a 64-bit hardware address is encountered.

- bpo-31848: Fix the error handling in Aifc_read.initfp() when the SSND chunk is not found. Patch by Zackery Spytz.

- bpo-32555: On FreeBSD and Solaris, os.strerror() now always decode the byte string from the current locale encoding, rather than using ASCII/surrogateescape in some cases.

- bpo-32521: The nis module is now compatible with new libnsl and headers location.

- bpo-32473: Improve ABCMeta._dump_registry() output readability

- bpo-32521: glibc has removed Sun RPC. Use replacement libtirpc headers and library in nis module.

- bpo-32228: Ensure that `truncate()` preserves the file position (as reported by `tell()`) after writes longer than the buffer size.

- bpo-26133: Don’t unsubscribe signals in asyncio UNIX event loop on interpreter shutdown.

- bpo-32185: The SSL module no longer sends IP addresses in SNI TLS extension on platforms with OpenSSL 1.0.2+ or inet_pton.

- bpo-32323: `urllib.parse.urlsplit()` does not convert zone-id (scope) to lower case for scoped IPv6 addresses in hostnames now.

- bpo-32302: Fix bdist_wininst of distutils for CRT v142: it binary compatible with CRT v140.

- bpo-32255: A single empty field is now always quoted when written into a CSV file. This allows to distinguish an empty row from a row consisting of a single empty field. Patch by Licht Takeuchi.

- bpo-32277: Raise `NotImplementedError` instead of `SystemError` on platforms where `chmod(..., follow_symlinks=False)` is not supported. Patch by Anthony Sottile.

- bpo-32199: The getnode() ip getter now uses ‘ip link’ instead of ‘ip link list’.

- bpo-27456: Ensure TCP_NODELAY is set on Linux. Tests by Victor Stinner.

- bpo-31900: The `locale.localeconv()` function now sets temporarily the `LC_CTYPE` locale to the `LC_NUMERIC` locale to decode `decimal_point` and `thousands_sep` byte strings if they are non-ASCII or longer than 1 byte, and the `LC_NUMERIC` locale is different than the `LC_CTYPE` locale. This temporary change affects other threads.

  Same change for the `str.format()` method when formatting a number (`int`, `float`, `float` and subclasses) with the `n` type (ex: `'{:n}'.format(1234)`).

- bpo-31802: Importing native path module (`posixpath`, `ntpath`) now works even if the `os` module still is not imported.

### Documentation

- bpo-17232: Clarify docs for -O and -OO. Patch by Terry Reedy.
- bpo-32800: Update link to w3c doc for xml default namespaces.
- bpo-8722: Document `__getattr__()` behavior when property `get()` method raises `AttributeError`.
- bpo-32614: Modify RE examples in documentation to use raw strings to prevent `DeprecationWarning` and add text to REGEX HOWTO to highlight the deprecation.
- bpo-31972: Improve docstrings for `pathlib.PurePath` subclasses.
- bpo-17799: Explain real behaviour of sys.settrace and sys.setprofile and their C-API counterparts regarding which type of events are received in each function. Patch by Pablo Galindo Salgado.

### Tests

- bpo-32517: Fix failing `test_asyncio` on macOS 10.12.2+ due to transport of `KqueueSelector` loop was not being closed.
- bpo-32721: Fix test_hashlib to not fail if the _md5 module is not built.
- bpo-32252: Fix faulthandler_suppress_crash_report() used to prevent core dump files when testing crashes. getrlimit() returns zero on success.
- bpo-31518: Debian Unstable has disabled TLS 1.0 and 1.1 for SSLv23_METHOD(). Change TLS/SSL protocol of some tests to PROTOCOL_TLS or PROTOCOL_TLSv1_2 to make them pass on Debian.

### Build

- bpo-32635: Fix segfault of the crypt module when libxcrypt is provided instead of libcrypt at the system.

### Windows

- bpo-33016: Fix potential use of uninitialized memory in nt._getfinalpathname
- bpo-32903: Fix a memory leak in os.chdir() on Windows if the current directory is set to a UNC path.
- bpo-31966: Fixed WindowsConsoleIO.write() for writing empty data.
- bpo-32409: Ensures activate.bat can handle Unicode contents.
- bpo-32457: Improves handling of denormalized executable path when launching Python.
- bpo-32370: Use the correct encoding for ipconfig output in the uuid module. Patch by Segev Finer.
- bpo-29248: Fix `os.readlink()` on Windows, which was mistakenly treating the `PrintNameOffset` field of the reparse data buffer as a number of characters instead of bytes. Patch by Craig Holmquist and SSE4.
- bpo-32588: Create standalone _distutils_findvs module.

### macOS

- bpo-32726: Provide an additional, more modern macOS installer variant that supports macOS 10.9+ systems in 64-bit mode only. Upgrade the supplied third-party libraries to OpenSSL 1.0.2n, XZ 5.2.3, and SQLite 3.22.0. The 10.9+ installer now links with and supplies its own copy of Tcl/Tk 8.6.8.

### IDLE

- bpo-32984: Set `__file__` while running a startup file. Like Python, IDLE optionally runs one startup file in the Shell window before presenting the first interactive input prompt. For IDLE, `-s` runs a file named in environmental variable `IDLESTARTUP` or `PYTHONSTARTUP`; `-r file` runs `file`. Python sets `__file__` to the startup file name before running the file and unsets it before the first prompt. IDLE now does the same when run normally, without the `-n` option.
- bpo-32940: Simplify and rename StringTranslatePseudoMapping in pyparse.
- bpo-32916: Change `str` to `code` in pyparse.
- bpo-32905: Remove unused code in pyparse module.
- bpo-32874: Add tests for pyparse.
- bpo-32837: Using the system and place-dependent default encoding for open() is a bad idea for IDLE’s system and location-independent files.
- bpo-32826: Add “encoding=utf-8” to open() in IDLE’s test_help_about. GUI test test_file_buttons() only looks at initial ascii-only lines, but failed on systems where open() defaults to ‘ascii’ because readline() internally reads and decodes far enough ahead to encounter a non-ascii character in CREDITS.txt.
- bpo-32765: Update configdialog General tab docstring to add new widgets to the widget list.

### Tools/Demos

- bpo-24960: 2to3 and lib2to3 can now read pickled grammar files using pkgutil.get_data() rather than probing the filesystem. This lets 2to3 and lib2to3 work when run from a zipfile.
- bpo-32222: Fix pygettext not extracting docstrings for functions with type annotated arguments. Patch by Toby Harradine.

### C API

- bpo-29084: Undocumented C API for OrderedDict has been excluded from the limited C API. It was added by mistake and actually never worked in the limited C API.

## Python 3.6.4 final

Release date: 2017-12-18

There were no new code changes in version 3.6.4 since v3.6.4rc1.

## Python 3.6.4 release candidate 1

Release date: 2017-12-05

### Core and Builtins

- bpo-32176: co_flags.CO_NOFREE is now always set correctly by the code object constructor based on freevars and cellvars, rather than needing to be set correctly by the caller. This ensures it will be cleared automatically when additional cell references are injected into a modified code object and function.
- bpo-31949: Fixed several issues in printing tracebacks (PyTraceBack_Print()).
  - Setting sys.tracebacklimit to 0 or less now suppresses printing tracebacks.
  - Setting sys.tracebacklimit to None now causes using the default limit.
  - Setting sys.tracebacklimit to an integer larger than LONG_MAX now means using the limit LONG_MAX rather than the default limit.
  - Fixed integer overflows in the case of more than 2**31 traceback items on Windows.
  - Fixed output errors handling.
- bpo-30696: Fix the interactive interpreter looping endlessly when no memory.
- bpo-20047: Bytearray methods partition() and rpartition() now accept only bytes-like objects as separator, as documented. In particular they now raise TypeError rather of returning a bogus result when an integer is passed as a separator.
- bpo-31852: Fix a segmentation fault caused by a combination of the async soft keyword and continuation lines.
- bpo-21720: BytesWarning no longer emitted when the fromlist argument of `__import__()` or the `__all__` attribute of the module contain bytes instances.
- bpo-31825: Fixed OverflowError in the ‘unicode-escape’ codec and in codecs.escape_decode() when decode an escaped non-ascii byte.
- bpo-28603: Print the full context/cause chain of exceptions on interpreter exit, even if an exception in the chain is unhashable or compares equal to later ones. Patch by Zane Bitter.
- bpo-31786: Fix timeout rounding in the select module to round correctly negative timeouts between -1.0 and 0.0. The functions now block waiting for events as expected. Previously, the call was incorrectly non-blocking. Patch by Pablo Galindo.
- bpo-31642: Restored blocking “from package import module” by setting sys.modules[“package.module”] to None.
- bpo-31626: Fixed a bug in debug memory allocator. There was a write to freed memory after shrinking a memory block.
- bpo-31619: Fixed a ValueError when convert a string with large number of underscores to integer with binary base.
- bpo-31592: Fixed an assertion failure in Python parser in case of a bad `unicodedata.normalize()`. Patch by Oren Milman.
- bpo-31588: Raise a `TypeError` with a helpful error message when class creation fails due to a metaclass with a bad `__prepare__()` method. Patch by Oren Milman.
- bpo-31566: Fix an assertion failure in `_warnings.warn()` in case of a bad `__name__` global. Patch by Oren Milman.
- bpo-31505: Fix an assertion failure in `json`, in case `_json.make_encoder()` received a bad `encoder()` argument. Patch by Oren Milman.
- bpo-31492: Fix assertion failures in case of failing to import from a module with a bad `__name__` attribute, and in case of failing to access an attribute of such a module. Patch by Oren Milman.
- bpo-31490: Fix an assertion failure in `ctypes` class definition, in case the class has an attribute whose name is specified in `_anonymous_` but not in `_fields_`. Patch by Oren Milman.
- bpo-31478: Fix an assertion failure in `_random.Random.seed()` in case the argument has a bad `__abs__()` method. Patch by Oren Milman.
- bpo-31315: Fix an assertion failure in imp.create_dynamic(), when spec.name is not a string. Patch by Oren Milman.
- bpo-31311: Fix a crash in the `__setstate__()` method of `ctypes._CData`, in case of a bad `__dict__`. Patch by Oren Milman.
- bpo-31293: Fix crashes in true division and multiplication of a timedelta object by a float with a bad as_integer_ratio() method. Patch by Oren Milman.
- bpo-31285: Fix an assertion failure in `warnings.warn_explicit`, when the return value of the received loader’s get_source() has a bad splitlines() method. Patch by Oren Milman.
- bpo-30817: `PyErr_PrintEx()` clears now the ignored exception that may be raised by `_PySys_SetObjectId()`, for example when no memory.

### Library

- bpo-28556: Two minor fixes for `typing` module: allow shallow copying instances of generic classes, improve interaction of `__init_subclass__` with generics. Original PRs by Ivan Levkivskyi.

- bpo-27240: The header folding algorithm for the new email policies has been rewritten, which also fixes bpo-30788, bpo-31831, and bpo-32182. In particular, RFC2231 folding is now done correctly.

- bpo-32186: io.FileIO.readall() and io.FileIO.read() now release the GIL when getting the file size. Fixed hang of all threads with inaccessible NFS server. Patch by Nir Soffer.

- bpo-12239: Make `msilib.SummaryInformation.GetProperty()` return `None` when the value of property is `VT_EMPTY`. Initial patch by Mark Mc Mahon.

- bpo-31325: Fix wrong usage of `collections.namedtuple()` in the `RobotFileParser.parse()` method.

  Initial patch by Robin Wellner.

- bpo-12382: `msilib.OpenDatabase()` now raises a better exception message when it couldn’t open or create an MSI file. Initial patch by William Tisäter.

- bpo-32110: `codecs.StreamReader.read(n)` now returns not more than n characters/bytes for non-negative n. This makes it compatible with `read()` methods of other file-like objects.

- bpo-32072: Fixed issues with binary plists:

  - Fixed saving bytearrays.
  - Identical objects will be saved only once.
  - Equal references will be load as identical objects.
  - Added support for saving and loading recursive data structures.

- bpo-32034: Make asyncio.IncompleteReadError and LimitOverrunError pickleable.

- bpo-32015: Fixed the looping of asyncio in the case of reconnection the socket during waiting async read/write from/to the socket.

- bpo-32011: Restored support of loading marshal files with the TYPE_INT64 code. These files can be produced in Python 2.7.

- bpo-31970: Reduce performance overhead of asyncio debug mode.

- bpo-9678: Fixed determining the MAC address in the uuid module:

  - Using ifconfig on NetBSD and OpenBSD.
  - Using arp on Linux, FreeBSD, NetBSD and OpenBSD.

  Based on patch by Takayuki Shimizukawa.

- bpo-30057: Fix potential missed signal in signal.signal().

- bpo-31933: Fix Blake2 params leaf_size and node_offset on big endian platforms. Patch by Jack O’Connor.

- bpo-31927: Fixed compilation of the socket module on NetBSD 8. Fixed assertion failure or reading arbitrary data when parse a AF_BLUETOOTH address on NetBSD and DragonFly BSD.

- bpo-27666: Fixed stack corruption in curses.box() and curses.ungetmouse() when the size of types chtype or mmask_t is less than the size of C long. curses.box() now accepts characters as arguments. Based on patch by Steve Fink.

- bpo-31897: plistlib now catches more errors when read binary plists and raises InvalidFileException instead of unexpected exceptions.

- bpo-25720: Fix the method for checking pad state of curses WINDOW. Patch by Masayuki Yamamoto.

- bpo-31893: Fixed the layout of the kqueue_event structure on OpenBSD and NetBSD. Fixed the comparison of the kqueue_event objects.

- bpo-31891: Fixed building the curses module on NetBSD.

- bpo-28416: Instances of pickle.Pickler subclass with the persistent_id() method and pickle.Unpickler subclass with the persistent_load() method no longer create reference cycles.

- bpo-28326: Fix multiprocessing.Process when stdout and/or stderr is closed or None.

- bpo-31457: If nested log adapters are used, the inner `process()` methods are no longer omitted.

- bpo-31457: The `manager` property on LoggerAdapter objects is now properly settable.

- bpo-31806: Fix timeout rounding in time.sleep(), threading.Lock.acquire() and socket.socket.settimeout() to round correctly negative timeouts between -1.0 and 0.0. The functions now block waiting for events as expected. Previously, the call was incorrectly non-blocking. Patch by Pablo Galindo.

- bpo-28603: traceback: Fix a TypeError that occurred during printing of exception tracebacks when either the current exception or an exception in its context/cause chain is unhashable. Patch by Zane Bitter.

- bpo-30058: Fixed buffer overflow in select.kqueue.control().

- bpo-31770: Prevent a crash when calling the `__init__()` method of a `sqlite3.Cursor` object more than once. Patch by Oren Milman.

- bpo-31672: `idpattern` in `string.Template` matched some non-ASCII characters. Now it uses `-i` regular expression local flag to avoid non-ASCII characters.

- bpo-31764: Prevent a crash in `sqlite3.Cursor.close()` in case the `Cursor` object is uninitialized. Patch by Oren Milman.

- bpo-31752: Fix possible crash in timedelta constructor called with custom integers.

- bpo-31701: On Windows, faulthandler.enable() now ignores MSC and COM exceptions.

- bpo-31728: Prevent crashes in `_elementtree` due to unsafe cleanup of `Element.text` and `Element.tail`. Patch by Oren Milman.

- bpo-31620: an empty asyncio.Queue now doesn’t leak memory when queue.get pollers timeout

- bpo-31632: Fix method set_protocol() of class _SSLProtocolTransport in asyncio module. This method was previously modifying a wrong reference to the protocol.

- bpo-31675: Fixed memory leaks in Tkinter’s methods splitlist() and split() when pass a string larger than 2 GiB.

- bpo-31673: Fixed typo in the name of Tkinter’s method adderrorinfo().

- bpo-30806: Fix the string representation of a netrc object.

- bpo-15037: Added a workaround for getkey() in curses for ncurses 5.7 and earlier.

- bpo-25351: Avoid venv activate failures with undefined variables

- bpo-25532: inspect.unwrap() will now only try to unwrap an object sys.getrecursionlimit() times, to protect against objects which create a new object on every attribute access.

- bpo-30347: Stop crashes when concurrently iterate over itertools.groupby() iterators.

- bpo-31516: `threading.current_thread()` should not return a dummy thread at shutdown.

- bpo-31351: python -m ensurepip now exits with non-zero exit code if pip bootstrapping has failed.

- bpo-31482: `random.seed()` now works with bytes in version=1

- bpo-31334: Fix `poll.poll([timeout])` in the `select` module for arbitrary negative timeouts on all OSes where it can only be a non-negative integer or -1. Patch by Riccardo Coccioli.

- bpo-31310: multiprocessing’s semaphore tracker should be launched again if crashed.

- bpo-31308: Make multiprocessing’s forkserver process immune to Ctrl-C and other user interruptions. If it crashes, restart it when necessary.

### Documentation

- bpo-32105: Added asyncio.BaseEventLoop.connect_accepted_socket versionadded marker.
- bpo-31537: Fix incorrect usage of `get_history_length` in readline documentation example code. Patch by Brad Smith.
- bpo-30085: The operator functions without double underscores are preferred for clarity. The one with underscores are only kept for back-compatibility.

### Tests

- bpo-31380: Skip test_httpservers test_undecodable_file on macOS: fails on APFS.
- bpo-31705: Skip test_socket.test_sha256() on Linux kernel older than 4.5. The test fails with ENOKEY on kernel 3.10 (on ppc64le). A fix was merged into the kernel 4.5.
- bpo-31174: Fix test_tools.test_unparse: DirectoryTestCase now stores the names sample to always test the same files. It prevents false alarms when hunting reference leaks.
- bpo-30695: Add the `set_nomemory(start, stop)` and `remove_mem_hooks()` functions to the _testcapi module.

### Build

- bpo-32059: `detect_modules()` in `setup.py` now also searches the sysroot paths when cross-compiling.
- bpo-31957: Fixes Windows SDK version detection when building for Windows.
- bpo-31609: Fixes quotes in PCbuild/clean.bat
- bpo-31934: Abort the build when building out of a not clean source tree.
- bpo-31926: Fixed Argument Clinic sometimes causing compilation errors when there was more than one function and/or method in a .c file with the same name.
- bpo-28791: Update Windows builds to use SQLite 3.21.0.
- bpo-28791: Update OS X installer to use SQLite 3.21.0.
- bpo-22140: Prevent double substitution of prefix in python-config.sh.
- bpo-31536: Avoid wholesale rebuild after `make regen-all` if nothing changed.

### Windows

- bpo-1102: Return `None` when `View.Fetch()` returns `ERROR_NO_MORE_ITEMS` instead of raising `MSIError`.

  Initial patch by Anthony Tuininga.

- bpo-31944: Fixes Modify button in Apps and Features dialog.

### macOS

- bpo-31392: Update macOS installer to use OpenSSL 1.0.2m

### IDLE

- bpo-32207: Improve tk event exception tracebacks in IDLE. When tk event handling is driven by IDLE’s run loop, a confusing and distracting queue.EMPTY traceback context is no longer added to tk event exception tracebacks. The traceback is now the same as when event handling is driven by user code. Patch based on a suggestion by Serhiy Storchaka.

- bpo-32164: Delete unused file idlelib/tabbedpages.py. Use of TabbedPageSet in configdialog was replaced by ttk.Notebook.

- bpo-32100: IDLE: Fix old and new bugs in pathbrowser; improve tests. Patch mostly by Cheryl Sabella.

- bpo-31858: IDLE – Restrict shell prompt manipulation to the shell. Editor and output windows only see an empty last prompt line. This simplifies the code and fixes a minor bug when newline is inserted. Sys.ps1, if present, is read on Shell start-up, but is not set or changed.

- bpo-31860: The font sample in the IDLE configuration dialog is now editable. Changes persist while IDLE remains open

- bpo-31836: Test_code_module now passes if run after test_idle, which sets ps1.

  The code module uses sys.ps1 if present or sets it to ‘>>> ‘ if not. Test_code_module now properly tests both behaviors. Ditto for ps2.

- bpo-28603: Fix a TypeError that caused a shell restart when printing a traceback that includes an exception that is unhashable. Patch by Zane Bitter.

- bpo-13802: Use non-Latin characters in the IDLE’s Font settings sample. Even if one selects a font that defines a limited subset of the unicode Basic Multilingual Plane, tcl/tk will use other fonts that define a character. The expanded example give users of non-Latin characters a better idea of what they might see in IDLE’s shell and editors. To make room for the expanded sample, frames on the Font tab are re-arranged. The Font/Tabs help explains a bit about the additions.

- bpo-31460: Simplify the API of IDLE’s Module Browser.

  Passing a widget instead of an flist with a root widget opens the option of creating a browser frame that is only part of a window. Passing a full file name instead of pieces assumed to come from a .py file opens the possibility of browsing python files that do not end in .py.

- bpo-31649: IDLE - Make _htest, _utest parameters keyword only.

- bpo-31559: Remove test order dependence in idle_test.test_browser.

- bpo-31459: Rename IDLE’s module browser from Class Browser to Module Browser. The original module-level class and method browser became a module browser, with the addition of module-level functions, years ago. Nested classes and functions were added yesterday. For back-compatibility, the virtual event <<open-class-browser>>, which appears on the Keys tab of the Settings dialog, is not changed. Patch by Cheryl Sabella.

- bpo-31500: Default fonts now are scaled on HiDPI displays.

- bpo-1612262: IDLE module browser now shows nested classes and functions. Original patches for code and tests by Guilherme Polo and Cheryl Sabella, respectively.

### Tools/Demos

- bpo-30722: Make redemo work with Python 3.6 and newer versions.

  Also, remove the `LOCALE` option since it doesn’t work with string patterns in Python 3.

  Patch by Christoph Sarnowski.

### C API

- bpo-20891: Fix PyGILState_Ensure(). When PyGILState_Ensure() is called in a non-Python thread before PyEval_InitThreads(), only call PyEval_InitThreads() after calling PyThreadState_New() to fix a crash.
- bpo-31532: Fix memory corruption due to allocator mix in getpath.c between Py_GetPath() and Py_SetPath()
- bpo-30697: The `PyExc_RecursionErrorInst` singleton is removed and `PyErr_NormalizeException()` does not use it anymore. This singleton is persistent and its members being never cleared may cause a segfault during finalization of the interpreter. See also bpo-22898.

## Python 3.6.3 final

Release date: 2017-10-03

### Library

- bpo-31641: Re-allow arbitrary iterables in `concurrent.futures.as_completed()`. Fixes regression in 3.6.3rc1.

### Build

- bpo-31662: Fix typos in Windows `uploadrelease.bat` script. Fix Windows Doc build issues in `Doc/make.bat`.
- bpo-31423: Fix building the PDF documentation with newer versions of Sphinx.

## Python 3.6.3 release candidate 1

Release date: 2017-09-18

### Security

- bpo-29781: SSLObject.version() now correctly returns None when handshake over BIO has not been performed yet.
- bpo-30947: Upgrade libexpat embedded copy from version 2.2.1 to 2.2.3 to get security fixes.

### Core and Builtins

- bpo-31471: Fix an assertion failure in `subprocess.Popen()` on Windows, in case the env argument has a bad keys() method. Patch by Oren Milman.

- bpo-31418: Fix an assertion failure in `PyErr_WriteUnraisable()` in case of an exception with a bad `__module__` attribute. Patch by Oren Milman.

- bpo-31416: Fix assertion failures in case of a bad warnings.filters or warnings.defaultaction. Patch by Oren Milman.

- bpo-31411: Raise a TypeError instead of SystemError in case warnings.onceregistry is not a dictionary. Patch by Oren Milman.

- bpo-31373: Fix several possible instances of undefined behavior due to floating-point demotions.

- bpo-30465: Location information (`lineno` and `col_offset`) in f-strings is now (mostly) correct. This fixes tools like flake8 from showing warnings on the wrong line (typically the first line of the file).

- bpo-31343: Include sys/sysmacros.h for major(), minor(), and makedev(). GNU C libray plans to remove the functions from sys/types.h.

- bpo-31291: Fix an assertion failure in `zipimport.zipimporter.get_data` on Windows, when the return value of `pathname.replace('/','\\')` isn’t a string. Patch by Oren Milman.

- bpo-31271: Fix an assertion failure in the write() method of `io.TextIOWrapper`, when the encoder doesn’t return a bytes object. Patch by Oren Milman.

- bpo-31243: Fix a crash in some methods of `io.TextIOWrapper`, when the decoder’s state is invalid. Patch by Oren Milman.

- bpo-30721: `print` now shows correct usage hint for using Python 2 redirection syntax. Patch by Sanyam Khurana.

- bpo-31070: Fix a race condition in importlib _get_module_lock().

- bpo-31095: Fix potential crash during GC caused by `tp_dealloc` which doesn’t call `PyObject_GC_UnTrack()`.

- bpo-31071: Avoid masking original TypeError in call with * unpacking when other arguments are passed.

- bpo-30978: str.format_map() now passes key lookup exceptions through. Previously any exception was replaced with a KeyError exception.

- bpo-30808: Use _Py_atomic API for concurrency-sensitive signal state.

- bpo-30876: Relative import from unloaded package now reimports the package instead of failing with SystemError. Relative import from non-package now fails with ImportError rather than SystemError.

- bpo-30703: Improve signal delivery.

  Avoid using Py_AddPendingCall from signal handler, to avoid calling signal-unsafe functions. The tests I’m adding here fail without the rest of the patch, on Linux and OS X. This means our signal delivery logic had defects (some signals could be lost).

- bpo-30765: Avoid blocking in pthread_mutex_lock() when PyThread_acquire_lock() is asked not to block.

- bpo-31161: Make sure the ‘Missing parentheses’ syntax error message is only applied to SyntaxError, not to subclasses. Patch by Martijn Pieters.

- bpo-30814: Fixed a race condition when import a submodule from a package.

- bpo-30597: `print` now shows expected input in custom error message when used as a Python 2 statement. Patch by Sanyam Khurana.

### Library

- bpo-31499: xml.etree: Fix a crash when a parser is part of a reference cycle.

- bpo-28556: typing.get_type_hints now finds the right globalns for classes and modules by default (when no `globalns` was specified by the caller).

- bpo-28556: Speed improvements to the `typing` module. Original PRs by Ivan Levkivskyi and Mitar.

- bpo-31544: The C accelerator module of ElementTree ignored exceptions raised when looking up TreeBuilder target methods in XMLParser().

- bpo-31234: socket.create_connection() now fixes manually a reference cycle: clear the variable storing the last exception on success.

- bpo-31457: LoggerAdapter objects can now be nested.

- bpo-31400: Improves SSL error handling to avoid losing error numbers.

- bpo-28958: ssl.SSLContext() now uses OpenSSL error information when a context cannot be instantiated.

- bpo-27340: SSLSocket.sendall() now uses memoryview to create slices of data. This fixes support for all bytes-like object. It is also more efficient and avoids costly copies.

- bpo-31178: Fix string concatenation bug in rare error path in the subprocess module

- bpo-31350: Micro-optimize `asyncio._get_running_loop()` to become up to 10% faster.

- bpo-31170: expat: Update libexpat from 2.2.3 to 2.2.4. Fix copying of partial characters for UTF-8 input (libexpat bug 115): https://github.com/libexpat/libexpat/issues/115

- bpo-29136: Add TLS 1.3 cipher suites and OP_NO_TLSv1_3.

- bpo-29212: Fix concurrent.futures.thread.ThreadPoolExecutor threads to have a non repr() based thread name by default when no thread_name_prefix is supplied. They will now identify themselves as “ThreadPoolExecutor-y_n”.

- bpo-9146: Fix a segmentation fault in _hashopenssl when standard hash functions such as md5 are not available in the linked OpenSSL library. As in some special FIPS-140 build environments.

- bpo-27144: The `map()` and `as_completed()` iterators in `concurrent.futures` now avoid keeping a reference to yielded objects.

- bpo-10746: Fix ctypes producing wrong PEP 3118 type codes for integer types.

- bpo-22536: The subprocess module now sets the filename when FileNotFoundError is raised on POSIX systems due to the executable or cwd not being found.

- bpo-31249: concurrent.futures: WorkItem.run() used by ThreadPoolExecutor now breaks a reference cycle between an exception object and the WorkItem object.

- bpo-31247: xmlrpc.server now explicitly breaks reference cycles when using sys.exc_info() in code handling exceptions.

- bpo-30102: The ssl and hashlib modules now call OPENSSL_add_all_algorithms_noconf() on OpenSSL < 1.1.0. The function detects CPU features and enables optimizations on some CPU architectures such as POWER8. Patch is based on research from Gustavo Serra Scalet.

- bpo-31185: Fixed miscellaneous errors in asyncio speedup module.

- bpo-31135: ttk: fix the destroy() method of LabeledScale and OptionMenu classes. Call the parent destroy() method even if the used attribute doesn’t exist. The LabeledScale.destroy() method now also explicitly clears label and scale attributes to help the garbage collector to destroy all widgets.

- bpo-31107: Fix `copyreg._slotnames()` mangled attribute calculation for classes whose name begins with an underscore. Patch by Shane Harvey.

- bpo-31061: Fixed a crash when using asyncio and threads.

- bpo-30502: Fix handling of long oids in ssl. Based on patch by Christian Heimes.

- bpo-30119: ftplib.FTP.putline() now throws ValueError on commands that contains CR or LF. Patch by Dong-hee Na.

- bpo-30595: multiprocessing.Queue.get() with a timeout now polls its reader in non-blocking mode if it succeeded to acquire the lock but the acquire took longer than the timeout.

- bpo-29403: Fix `unittest.mock`’s autospec to not fail on method-bound builtin functions. Patch by Aaron Gallagher.

- bpo-30961: Fix decrementing a borrowed reference in tracemalloc.

- bpo-25684: Change `ttk.OptionMenu` radiobuttons to be unique across instances of `OptionMenu`.

- bpo-30886: Fix multiprocessing.Queue.join_thread(): it now waits until the thread completes, even if the thread was started by the same process which created the queue.

- bpo-29854: Fix segfault in readline when using readline’s history-size option. Patch by Nir Soffer.

- bpo-30319: socket.close() now ignores ECONNRESET error.

- bpo-30828: Fix out of bounds write in `asyncio.CFuture.remove_done_callback()`.

- bpo-30807: signal.setitimer() may disable the timer when passed a tiny value.

  Tiny values (such as 1e-6) are valid non-zero values for setitimer(), which is specified as taking microsecond-resolution intervals. However, on some platform, our conversion routine could convert 1e-6 into a zero interval, therefore disabling the timer instead of (re-)scheduling it.

- bpo-30441: Fix bug when modifying os.environ while iterating over it

- bpo-30532: Fix email header value parser dropping folding white space in certain cases.

- bpo-30879: os.listdir() and os.scandir() now emit bytes names when called with bytes-like argument.

- bpo-30746: Prohibited the ‘=’ character in environment variable names in `os.putenv()` and `os.spawn*()`.

- bpo-29755: Fixed the lgettext() family of functions in the gettext module. They now always return bytes.

### Documentation

- bpo-31294: Fix incomplete code snippet in the ZeroMQSocketListener and ZeroMQSocketHandler examples and adapt them to Python 3.
- bpo-21649: Add RFC 7525 and Mozilla server side TLS links to SSL documentation.
- bpo-30803: Clarify doc on truth value testing. Original patch by Peter Thomassen.

### Tests

- bpo-31320: Silence traceback in test_ssl
- bpo-25674: Remove sha256.tbs-internet.com ssl test
- bpo-30715: Address ALPN callback changes for OpenSSL 1.1.0f. The latest version behaves like OpenSSL 1.0.2 and no longer aborts handshake.
- bpo-30822: regrtest: Exclude tzdata from regrtest –all. When running the test suite using –use=all / -u all, exclude tzdata since it makes test_datetime too slow (15-20 min on some buildbots) which then times out on some buildbots. Fix also regrtest command line parser to allow passing -u extralargefile to run test_zipfile64.

### Build

- bpo-30854: Fix compile error when compiling –without-threads. Patch by Masayuki Yamamoto.

### Windows

- bpo-30389: Adds detection of Visual Studio 2017 to distutils on Windows.
- bpo-31340: Change to building with MSVC v141 (included with Visual Studio 2017)
- bpo-30581: os.cpu_count() now returns the correct number of processors on Windows when the number of logical processors is greater than 64.
- bpo-30731: Add a missing xmlns to python.manifest so that it matches the schema.

### IDLE

- bpo-31493: IDLE code context – fix code update and font update timers.

  Canceling timers prevents a warning message when test_idle completes.

- bpo-31488: IDLE - Update non-key options in former extension classes. When applying configdialog changes, call .reload for each feature class. Change ParenMatch so updated options affect existing instances attached to existing editor windows.

- bpo-31477: IDLE - Improve rstrip entry in doc. Strip trailing whitespace strips more than blank spaces. Multiline string literals are not skipped.

- bpo-31480: IDLE - make tests pass with zzdummy extension disabled by default.

- bpo-31421: Document how IDLE runs tkinter programs. IDLE calls tcl/tk update in the background in order to make live

  interaction and experimentation with tkinter applications much easier.

- bpo-31414: IDLE – fix tk entry box tests by deleting first. Adding to an int entry is not the same as deleting and inserting because int(‘’) will fail.

- bpo-31051: Rearrange IDLE configdialog GenPage into Window, Editor, and Help sections.

- bpo-30617: IDLE - Add docstrings and tests for outwin subclass of editor.

  Move some data and functions from the class to module level. Patch by Cheryl Sabella.

- bpo-31287: IDLE - Do not modify tkinter.message in test_configdialog.

- bpo-27099: Convert IDLE’s built-in ‘extensions’ to regular features.

  About 10 IDLE features were implemented as supposedly optional extensions. Their different behavior could be confusing or worse for users and not good for maintenance. Hence the conversion.

  The main difference for users is that user configurable key bindings for builtin features are now handled uniformly. Now, editing a binding in a keyset only affects its value in the keyset. All bindings are defined together in the system-specific default keysets in config-extensions.def. All custom keysets are saved as a whole in config-extension.cfg. All take effect as soon as one clicks Apply or Ok.

  The affected events are ‘<<force-open-completions>>’, ‘<<expand-word>>’, ‘<<force-open-calltip>>’, ‘<<flash-paren>>’, ‘<<format-paragraph>>’, ‘<<run-module>>’, ‘<<check-module>>’, and ‘<<zoom-height>>’. Any (global) customizations made before 3.6.3 will not affect their keyset-specific customization after 3.6.3. and vice versa.

  Inital patch by Charles Wohlganger.

- bpo-31206: IDLE: Factor HighPage(Frame) class from ConfigDialog. Patch by Cheryl Sabella.

- bpo-31001: Add tests for configdialog highlight tab. Patch by Cheryl Sabella.

- bpo-31205: IDLE: Factor KeysPage(Frame) class from ConfigDialog. The slightly modified tests continue to pass. Patch by Cheryl Sabella.

- bpo-31130: IDLE – stop leaks in test_configdialog. Initial patch by Victor Stinner.

- bpo-31002: Add tests for configdialog keys tab. Patch by Cheryl Sabella.

- bpo-19903: IDLE: Calltips use `inspect.signature` instead of `inspect.getfullargspec`. This improves calltips for builtins converted to use Argument Clinic. Patch by Louie Lu.

- bpo-31083: IDLE - Add an outline of a TabPage class in configdialog. Update existing classes to match outline. Initial patch by Cheryl Sabella.

- bpo-31050: Factor GenPage(Frame) class from ConfigDialog. The slightly modified tests continue to pass. Patch by Cheryl Sabella.

- bpo-31004: IDLE - Factor FontPage(Frame) class from ConfigDialog.

  Slightly modified tests continue to pass. Fix General tests. Patch mostly by Cheryl Sabella.

- bpo-30781: IDLE - Use ttk widgets in ConfigDialog. Patches by Terry Jan Reedy and Cheryl Sabella.

- bpo-31060: IDLE - Finish rearranging methods of ConfigDialog Grouping methods pertaining to each tab and the buttons will aid writing tests and improving the tabs and will enable splitting the groups into classes.

- bpo-30853: IDLE – Factor a VarTrace class out of ConfigDialog.

  Instance tracers manages pairs consisting of a tk variable and a callback function. When tracing is turned on, setting the variable calls the function. Test coverage for the new class is 100%.

- bpo-31003: IDLE: Add more tests for General tab.

- bpo-30993: IDLE - Improve configdialog font page and tests.

  In configdialog: Document causal pathways in create_font_tab docstring. Simplify some attribute names. Move set_samples calls to var_changed_font (idea from Cheryl Sabella). Move related functions to positions after the create widgets function.

  In test_configdialog: Fix test_font_set so not order dependent. Fix renamed test_indent_scale so it tests the widget. Adjust tests for movement of set_samples call. Add tests for load functions. Put all font tests in one class and tab indent tests in another. Except for two lines, these tests completely cover the related functions.

- bpo-30981: IDLE – Add more configdialog font page tests.

- bpo-28523: IDLE: replace ‘colour’ with ‘color’ in configdialog.

- bpo-30917: Add tests for idlelib.config.IdleConf. Increase coverage from 46% to 96%. Patch by Louie Lu.

- bpo-30934: Document coverage details for idlelib tests.

  - Add section to idlelib/idle-test/README.txt.
  - Include check that branches are taken both ways.
  - Exclude IDLE-specific code that does not run during unit tests.

- bpo-30913: IDLE: Document ConfigDialog tk Vars, methods, and widgets in docstrings This will facilitate improving the dialog and splitting up the class. Original patch by Cheryl Sabella.

- bpo-30899: IDLE: Add tests for ConfigParser subclasses in config. Patch by Louie Lu.

- bpo-30881: IDLE: Add docstrings to browser.py. Patch by Cheryl Sabella.

- bpo-30851: IDLE: Remove unused variables in configdialog. One is a duplicate, one is set but cannot be altered by users. Patch by Cheryl Sabella.

- bpo-30870: IDLE: In Settings dialog, select font with Up, Down keys as well as mouse. Initial patch by Louie Lu.

- bpo-8231: IDLE: call config.IdleConf.GetUserCfgDir only once.

- bpo-30779: IDLE: Factor ConfigChanges class from configdialog, put in config; test. * In config, put dump test code in a function; run it and unittest in ‘if __name__ == ‘__main__’. * Add class config.ConfigChanges based on changes_class_v4.py on bpo issue. * Add class test_config.ChangesTest, partly using configdialog_tests_v1.py. * Revise configdialog to use ConfigChanges; see tracker msg297804. * Revise test_configdialog to match configdialog changes. * Remove configdialog functions unused or moved to ConfigChanges. Cheryl Sabella contributed parts of the patch.

- bpo-30777: IDLE: configdialog - Add docstrings and fix comments. Patch by Cheryl Sabella.

- bpo-30495: IDLE: Improve textview with docstrings, PEP8 names, and more tests. Patch by Cheryl Sabella.

- bpo-30723: IDLE: Make several improvements to parenmatch. Add ‘parens’ style to highlight both opener and closer. Make ‘default’ style, which is not default, a synonym for ‘opener’. Make time-delay work the same with all styles. Add help for config dialog extensions tab, including help for parenmatch. Add new tests. Original patch by Charles Wohlganger.

- bpo-30674: IDLE: add docstrings to grep module. Patch by Cheryl Sabella

- bpo-21519: IDLE’s basic custom key entry dialog now detects duplicates properly. Original patch by Saimadhav Heblikar.

- bpo-29910: IDLE no longer deletes a character after commenting out a region by a key shortcut. Add `return 'break'` for this and other potential conflicts between IDLE and default key bindings.

- bpo-30728: Review and change idlelib.configdialog names. Lowercase method and attribute names. Replace ‘colour’ with ‘color’, expand overly cryptic names, delete unneeded underscores. Replace `import *` with specific imports. Patches by Cheryl Sabella.

- bpo-6739: IDLE: Verify user-entered key sequences by trying to bind them with tk. Add tests for all 3 validation functions. Original patch by G Polo. Tests added by Cheryl Sabella.

### Tools/Demos

- bpo-30983: gdb integration commands (py-bt, etc.) work on optimized shared builds now, too. PEP 523 introduced _PyEval_EvalFrameDefault which inlines PyEval_EvalFrameEx on non-debug shared builds. This broke the ability to use py-bt, py-up, and a few other Python-specific gdb integrations. The problem is fixed by only looking for _PyEval_EvalFrameDefault frames in python-gdb.py. Original patch by Bruno “Polaco” Penteado.

## Python 3.6.2 final

Release date: 2017-07-17

No changes since release candidate 2

## Python 3.6.2 release candidate 2

Release date: 2017-07-07

### Security

- bpo-30730: Prevent environment variables injection in subprocess on Windows. Prevent passing other environment variables and command arguments.
- bpo-30694: Upgrade expat copy from 2.2.0 to 2.2.1 to get fixes of multiple security vulnerabilities including: CVE-2017-9233 (External entity infinite loop DoS), CVE-2016-9063 (Integer overflow, re-fix), CVE-2016-0718 (Fix regression bugs from 2.2.0’s fix to CVE-2016-0718) and CVE-2012-0876 (Counter hash flooding with SipHash). Note: the CVE-2016-5300 (Use os-specific entropy sources like getrandom) doesn’t impact Python, since Python already gets entropy from the OS to set the expat secret using `XML_SetHashSalt()`.
- bpo-30500: Fix urllib.parse.splithost() to correctly parse fragments. For example, `splithost('//127.0.0.1#@evil.com/')` now correctly returns the `127.0.0.1` host, instead of treating `@evil.com` as the host in an authentication (`login@host`).

## Python 3.6.2 release candidate 1

Release date: 2017-06-17

### Core and Builtins

- bpo-30682: Removed a too-strict assertion that failed for certain f-strings, such as eval(“f’\n’”) and eval(“f’\r’”).
- bpo-30604: Move co_extra_freefuncs to not be per-thread to avoid crashes
- bpo-29104: Fixed parsing backslashes in f-strings.
- bpo-27945: Fixed various segfaults with dict when input collections are mutated during searching, inserting or comparing. Based on patches by Duane Griffin and Tim Mitchell.
- bpo-25794: Fixed type.__setattr__() and type.__delattr__() for non-interned attribute names. Based on patch by Eryk Sun.
- bpo-30039: If a KeyboardInterrupt happens when the interpreter is in the middle of resuming a chain of nested ‘yield from’ or ‘await’ calls, it’s now correctly delivered to the innermost frame.
- bpo-12414: sys.getsizeof() on a code object now returns the sizes which includes the code struct and sizes of objects which it references. Patch by Dong-hee Na.
- bpo-29949: Fix memory usage regression of set and frozenset object.
- bpo-29935: Fixed error messages in the index() method of tuple, list and deque when pass indices of wrong type.
- bpo-29859: Show correct error messages when any of the pthread_* calls in thread_pthread.h fails.
- bpo-28876: `bool(range)` works even if `len(range)` raises `OverflowError`.
- bpo-29600: Fix wrapping coroutine return values in StopIteration.
- bpo-28856: Fix an oversight that %b format for bytes should support objects follow the buffer protocol.
- bpo-29714: Fix a regression that bytes format may fail when containing zero bytes inside.
- bpo-29478: If max_line_length=None is specified while using the Compat32 policy, it is no longer ignored. Patch by Mircea Cosbuc.

### Library

- bpo-30616: Functional API of enum allows to create empty enums. Patched by Dong-hee Na
- bpo-30038: Fix race condition between signal delivery and wakeup file descriptor. Patch by Nathaniel Smith.
- bpo-23894: lib2to3 now recognizes `rb'...'` and `f'...'` strings.
- bpo-23890: unittest.TestCase.assertRaises() now manually breaks a reference cycle to not keep objects alive longer than expected.
- bpo-30149: inspect.signature() now supports callables with variable-argument parameters wrapped with partialmethod. Patch by Dong-hee Na.
- bpo-30645: Fix path calculation in imp.load_package(), fixing it for cases when a package is only shipped with bytecodes. Patch by Alexandru Ardelean.
- bpo-29931: Fixed comparison check for ipaddress.ip_interface objects. Patch by Sanjay Sundaresan.
- bpo-30605: re.compile() no longer raises a BytesWarning when compiling a bytes instance with misplaced inline modifier. Patch by Roy Williams.

### Security

- bpo-29591: Update expat copy from 2.1.1 to 2.2.0 to get fixes of CVE-2016-0718 and CVE-2016-4472. See https://sourceforge.net/p/expat/bugs/537/ for more information.

### Library

- bpo-24484: Avoid race condition in multiprocessing cleanup (#2159)
- bpo-28994: The traceback no longer displayed for SystemExit raised in a callback registered by atexit.
- bpo-30508: Don’t log exceptions if Task/Future “cancel()” method was called.
- bpo-28556: Updates to typing module: Add generic AsyncContextManager, add support for ContextManager on all versions. Original PRs by Jelle Zijlstra and Ivan Levkivskyi
- bpo-29870: Fix ssl sockets leaks when connection is aborted in asyncio/ssl implementation. Patch by Michaël Sghaïer.
- bpo-29743: Closing transport during handshake process leaks open socket. Patch by Nikolay Kim
- bpo-27585: Fix waiter cancellation in asyncio.Lock. Patch by Mathieu Sornay.
- bpo-30418: On Windows, subprocess.Popen.communicate() now also ignore EINVAL on stdin.write() if the child process is still running but closed the pipe.
- bpo-29822: inspect.isabstract() now works during __init_subclass__. Patch by Nate Soares.
- bpo-29581: ABCMeta.__new__ now accepts `**kwargs`, allowing abstract base classes to use keyword parameters in __init_subclass__. Patch by Nate Soares.
- bpo-30557: faulthandler now correctly filters and displays exception codes on Windows
- bpo-30378: Fix the problem that logging.handlers.SysLogHandler cannot handle IPv6 addresses.
- bpo-29960: Preserve generator state when _random.Random.setstate() raises an exception. Patch by Bryan Olson.
- bpo-30414: multiprocessing.Queue._feed background running thread do not break from main loop on exception.
- bpo-30003: Fix handling escape characters in HZ codec. Based on patch by Ma Lin.
- bpo-30301: Fix AttributeError when using SimpleQueue.empty() under spawn and forkserver start methods.
- bpo-30329: imaplib and poplib now catch the Windows socket WSAEINVAL error (code 10022) on shutdown(SHUT_RDWR): An invalid operation was attempted. This error occurs sometimes on SSL connections.
- bpo-30375: Warnings emitted when compile a regular expression now always point to the line in the user code. Previously they could point into inners of the re module if emitted from inside of groups or conditionals.
- bpo-30048: Fixed `Task.cancel()` can be ignored when the task is running coroutine and the coroutine returned without any more `await`.
- bpo-30266: contextlib.AbstractContextManager now supports anti-registration by setting __enter__ = None or __exit__ = None, following the pattern introduced in bpo-25958. Patch by Jelle Zijlstra.
- bpo-30298: Weaken the condition of deprecation warnings for inline modifiers. Now allowed several subsequential inline modifiers at the start of the pattern (e.g. `'(?i)(?s)...'`). In verbose mode whitespaces and comments now are allowed before and between inline modifiers (e.g. `'(?x) (?i) (?s)...'`).
- bpo-29990: Fix range checking in GB18030 decoder. Original patch by Ma Lin.
- bpo-26293: Change resulted because of zipfile breakage. (See also: bpo-29094)
- bpo-30243: Removed the __init__ methods of _json’s scanner and encoder. Misusing them could cause memory leaks or crashes. Now scanner and encoder objects are completely initialized in the __new__ methods.
- bpo-30185: Avoid KeyboardInterrupt tracebacks in forkserver helper process when Ctrl-C is received.
- bpo-28556: Various updates to typing module: add typing.NoReturn type, use WrapperDescriptorType, minor bug-fixes. Original PRs by Jim Fasarakis-Hilliard and Ivan Levkivskyi.
- bpo-30205: Fix getsockname() for unbound AF_UNIX sockets on Linux.
- bpo-30070: Fixed leaks and crashes in errors handling in the parser module.
- bpo-30061: Fixed crashes in IOBase methods __next__() and readlines() when readline() or __next__() respectively return non-sizeable object. Fixed possible other errors caused by not checking results of PyObject_Size(), PySequence_Size(), or PyMapping_Size().
- bpo-30017: Allowed calling the close() method of the zip entry writer object multiple times. Writing to a closed writer now always produces a ValueError.
- bpo-30068: _io._IOBase.readlines will check if it’s closed first when hint is present.
- bpo-29694: Fixed race condition in pathlib mkdir with flags parents=True. Patch by Armin Rigo.
- bpo-29692: Fixed arbitrary unchaining of RuntimeError exceptions in contextlib.contextmanager. Patch by Siddharth Velankar.
- bpo-29998: Pickling and copying ImportError now preserves name and path attributes.
- bpo-29953: Fixed memory leaks in the replace() method of datetime and time objects when pass out of bound fold argument.
- bpo-29942: Fix a crash in itertools.chain.from_iterable when encountering long runs of empty iterables.
- bpo-27863: Fixed multiple crashes in ElementTree caused by race conditions and wrong types.
- bpo-28699: Fixed a bug in pools in multiprocessing.pool that raising an exception at the very first of an iterable may swallow the exception or make the program hang. Patch by Davin Potts and Xiang Zhang.
- bpo-25803: Avoid incorrect errors raised by Path.mkdir(exist_ok=True) when the OS gives priority to errors such as EACCES over EEXIST.
- bpo-29861: Release references to tasks, their arguments and their results as soon as they are finished in multiprocessing.Pool.
- bpo-29884: faulthandler: Restore the old sigaltstack during teardown. Patch by Christophe Zeitouny.
- bpo-25455: Fixed crashes in repr of recursive buffered file-like objects.
- bpo-29800: Fix crashes in partial.__repr__ if the keys of partial.keywords are not strings. Patch by Michael Seifert.
- bpo-29742: get_extra_info() raises exception if get called on closed ssl transport. Patch by Nikolay Kim.
- bpo-8256: Fixed possible failing or crashing input() if attributes “encoding” or “errors” of sys.stdin or sys.stdout are not set or are not strings.
- bpo-28298: Fix a bug that prevented array ‘Q’, ‘L’ and ‘I’ from accepting big intables (objects that have __int__) as elements. Patch by Oren Milman.
- bpo-28231: The zipfile module now accepts path-like objects for external paths.
- bpo-26915: index() and count() methods of collections.abc.Sequence now check identity before checking equality when do comparisons.
- bpo-29615: SimpleXMLRPCDispatcher no longer chains KeyError (or any other exception) to exception(s) raised in the dispatched methods. Patch by Petr Motejlek.
- bpo-30177: path.resolve(strict=False) no longer cuts the path after the first element not present in the filesystem. Patch by Antoine Pietri.

### IDLE

- bpo-15786: Fix several problems with IDLE’s autocompletion box. The following should now work: clicking on selection box items; using the scrollbar; selecting an item by hitting Return. Hangs on MacOSX should no longer happen. Patch by Louie Lu.
- bpo-25514: Add doc subsubsection about IDLE failure to start. Popup no-connection message directs users to this section.
- bpo-30642: Fix reference leaks in IDLE tests. Patches by Louie Lu and Terry Jan Reedy.
- bpo-30495: Add docstrings for textview.py and use PEP8 names. Patches by Cheryl Sabella and Terry Jan Reedy.
- bpo-30290: Help-about: use pep8 names and add tests. Increase coverage to 100%. Patches by Louie Lu, Cheryl Sabella, and Terry Jan Reedy.
- bpo-30303: Add _utest option to textview; add new tests. Increase coverage to 100%. Patches by Louie Lu and Terry Jan Reedy.

### C API

- bpo-27867: Function PySlice_GetIndicesEx() no longer replaced with a macro if Py_LIMITED_API is not set.

### Build

- bpo-29941: Add `--with-assertions` configure flag to explicitly enable C `assert()` checks. Defaults to off. `--with-pydebug` implies `--with-assertions`.
- bpo-28787: Fix out-of-tree builds of Python when configured with `--with--dtrace`.
- bpo-29243: Prevent unnecessary rebuilding of Python during `make test`, `make install` and some other make targets when configured with `--enable-optimizations`.
- bpo-23404: Don’t regenerate generated files based on file modification time anymore: the action is now explicit. Replace `make touch` with `make regen-all`.
- bpo-29643: Fix `--enable-optimization` didn’t work.

### Documentation

- bpo-30176: Add missing attribute related constants in curses documentation.

- bpo-30052: the link targets for `bytes()` and `bytearray()` are now their respective type definitions, rather than the corresponding builtin function entries. Use bytes and bytearray to reference the latter.

  In order to ensure this and future cross-reference updates are applied automatically, the daily documentation builds now disable the default output caching features in Sphinx.

- bpo-26985: Add missing info of code object in inspect documentation.

### Tools/Demos

- bpo-29367: python-gdb.py now supports also `method-wrapper` (`wrapperobject`) objects.

### Tests

- bpo-30357: test_thread: setUp() now uses support.threading_setup() and support.threading_cleanup() to wait until threads complete to avoid random side effects on following tests. Initial patch written by Grzegorz Grzywacz.
- bpo-30197: Enhanced functions swap_attr() and swap_item() in the test.support module. They now work when delete replaced attribute or item inside the with statement. The old value of the attribute or item (or None if it doesn’t exist) now will be assigned to the target of the “as” clause, if there is one.

### Windows

- bpo-30687: Locate msbuild.exe on Windows when building rather than vcvarsall.bat
- bpo-30450: The build process on Windows no longer depends on Subversion, instead pulling external code from GitHub via a Python script. If Python 3.6 is not found on the system (via `py -3.6`), NuGet is used to download a copy of 32-bit Python.

## Python 3.6.1 final

Release date: 2017-03-21

### Core and Builtins

- bpo-29723: The `sys.path[0]` initialization change for bpo-29139 caused a regression by revealing an inconsistency in how sys.path is initialized when executing `__main__` from a zipfile, directory, or other import location. The interpreter now consistently avoids ever adding the import location’s parent directory to `sys.path`, and ensures no other `sys.path` entries are inadvertently modified when inserting the import location named on the command line.

### Build

- bpo-27593: fix format of git information used in sys.version
- Fix incompatible comment in python.h

## Python 3.6.1 release candidate 1

Release date: 2017-03-04

### Core and Builtins

- bpo-28893: Set correct __cause__ for errors about invalid awaitables returned from __aiter__ and __anext__.
- bpo-29683: Fixes to memory allocation in _PyCode_SetExtra. Patch by Brian Coleman.
- bpo-29684: Fix minor regression of PyEval_CallObjectWithKeywords. It should raise TypeError when kwargs is not a dict. But it might cause segv when args=NULL and kwargs is not a dict.
- bpo-28598: Support __rmod__ for subclasses of str being called before str.__mod__. Patch by Martijn Pieters.
- bpo-29607: Fix stack_effect computation for CALL_FUNCTION_EX. Patch by Matthieu Dartiailh.
- bpo-29602: Fix incorrect handling of signed zeros in complex constructor for complex subclasses and for inputs having a __complex__ method. Patch by Serhiy Storchaka.
- bpo-29347: Fixed possibly dereferencing undefined pointers when creating weakref objects.
- bpo-29438: Fixed use-after-free problem in key sharing dict.
- bpo-29319: Prevent RunMainFromImporter overwriting sys.path[0].
- bpo-29337: Fixed possible BytesWarning when compare the code objects. Warnings could be emitted at compile time.
- bpo-29327: Fixed a crash when pass the iterable keyword argument to sorted().
- bpo-29034: Fix memory leak and use-after-free in os module (path_converter).
- bpo-29159: Fix regression in bytes(x) when x.__index__() raises Exception.
- bpo-28932: Do not include <sys/random.h> if it does not exist.
- bpo-25677: Correct the positioning of the syntax error caret for indented blocks. Based on patch by Michael Layzell.
- bpo-29000: Fixed bytes formatting of octals with zero padding in alternate form.
- bpo-26919: On Android, operating system data is now always encoded/decoded to/from UTF-8, instead of the locale encoding to avoid inconsistencies with os.fsencode() and os.fsdecode() which are already using UTF-8.
- bpo-28991: functools.lru_cache() was susceptible to an obscure reentrancy bug triggerable by a monkey-patched len() function.
- bpo-28739: f-string expressions are no longer accepted as docstrings and by ast.literal_eval() even if they do not include expressions.
- bpo-28512: Fixed setting the offset attribute of SyntaxError by PyErr_SyntaxLocationEx() and PyErr_SyntaxLocationObject().
- bpo-28918: Fix the cross compilation of xxlimited when Python has been built with Py_DEBUG defined.
- bpo-28731: Optimize _PyDict_NewPresized() to create correct size dict. Improve speed of dict literal with constant keys up to 30%.

### Library

- bpo-29169: Update zlib to 1.2.11.
- bpo-29623: Allow use of path-like object as a single argument in ConfigParser.read(). Patch by David Ellis.
- bpo-28963: Fix out of bound iteration in asyncio.Future.remove_done_callback implemented in C.
- bpo-29704: asyncio.subprocess.SubprocessStreamProtocol no longer closes before all pipes are closed.
- bpo-29271: Fix Task.current_task and Task.all_tasks implemented in C to accept None argument as their pure Python implementation.
- bpo-29703: Fix asyncio to support instantiation of new event loops in child processes.
- bpo-29376: Fix assertion error in threading._DummyThread.is_alive().
- bpo-28624: Add a test that checks that cwd parameter of Popen() accepts PathLike objects. Patch by Sayan Chowdhury.
- bpo-28518: Start a transaction implicitly before a DML statement. Patch by Aviv Palivoda.
- bpo-29532: Altering a kwarg dictionary passed to functools.partial() no longer affects a partial object after creation.
- bpo-29110: Fix file object leak in aifc.open() when file is given as a filesystem path and is not in valid AIFF format. Patch by Anthony Zhang.
- bpo-28556: Various updates to typing module: typing.Counter, typing.ChainMap, improved ABC caching, etc. Original PRs by Jelle Zijlstra, Ivan Levkivskyi, Manuel Krebber, and Łukasz Langa.
- bpo-29100: Fix datetime.fromtimestamp() regression introduced in Python 3.6.0: check minimum and maximum years.
- bpo-29519: Fix weakref spewing exceptions during interpreter shutdown when used with a rare combination of multiprocessing and custom codecs.
- bpo-29416: Prevent infinite loop in pathlib.Path.mkdir
- bpo-29444: Fixed out-of-bounds buffer access in the group() method of the match object. Based on patch by WGH.
- bpo-29335: Fix subprocess.Popen.wait() when the child process has exited to a stopped instead of terminated state (ex: when under ptrace).
- bpo-29290: Fix a regression in argparse that help messages would wrap at non-breaking spaces.
- bpo-28735: Fixed the comparison of mock.MagickMock with mock.ANY.
- bpo-29316: Restore the provisional status of typing module, add corresponding note to documentation. Patch by Ivan L.
- bpo-29219: Fixed infinite recursion in the repr of uninitialized ctypes.CDLL instances.
- bpo-29011: Fix an important omission by adding Deque to the typing module.
- bpo-28969: Fixed race condition in C implementation of functools.lru_cache. KeyError could be raised when cached function with full cache was simultaneously called from differen threads with the same uncached arguments.
- bpo-29142: In urllib.request, suffixes in no_proxy environment variable with leading dots could match related hostnames again (e.g. .b.c matches a.b.c). Patch by Milan Oberkirch.
- bpo-28961: Fix unittest.mock._Call helper: don’t ignore the name parameter anymore. Patch written by Jiajun Huang.
- bpo-29203: functools.lru_cache() now respects PEP 468 and preserves the order of keyword arguments. f(a=1, b=2) is now cached separately from f(b=2, a=1) since both calls could potentially give different results.
- bpo-15812: inspect.getframeinfo() now correctly shows the first line of a context. Patch by Sam Breese.
- bpo-29094: Offsets in a ZIP file created with extern file object and modes “w” and “x” now are relative to the start of the file.
- bpo-29085: Allow random.Random.seed() to use high quality OS randomness rather than the pid and time.
- bpo-29061: Fixed bug in secrets.randbelow() which would hang when given a negative input. Patch by Brendan Donegan.
- bpo-29079: Prevent infinite loop in pathlib.resolve() on Windows
- bpo-13051: Fixed recursion errors in large or resized curses.textpad.Textbox. Based on patch by Tycho Andersen.
- bpo-29119: Fix weakrefs in the pure python version of collections.OrderedDict move_to_end() method. Contributed by Andra Bogildea.
- bpo-9770: curses.ascii predicates now work correctly with negative integers.
- bpo-28427: old keys should not remove new values from WeakValueDictionary when collecting from another thread.
- bpo-28923: Remove editor artifacts from Tix.py.
- bpo-29055: Neaten-up empty population error on random.choice() by suppressing the upstream exception.
- bpo-28871: Fixed a crash when deallocate deep ElementTree.
- bpo-19542: Fix bugs in WeakValueDictionary.setdefault() and WeakValueDictionary.pop() when a GC collection happens in another thread.
- bpo-20191: Fixed a crash in resource.prlimit() when passing a sequence that doesn’t own its elements as limits.
- bpo-28779: multiprocessing.set_forkserver_preload() would crash the forkserver process if a preloaded module instantiated some multiprocessing objects such as locks.
- bpo-28847: dbm.dumb now supports reading read-only files and no longer writes the index file when it is not changed.
- bpo-26937: The chown() method of the tarfile.TarFile class does not fail now when the grp module cannot be imported, as for example on Android platforms.

### IDLE

- bpo-29071: IDLE colors f-string prefixes (but not invalid ur prefixes).
- bpo-28572: Add 10% to coverage of IDLE’s test_configdialog. Update and augment description of the configuration system.

### Windows

- bpo-29579: Removes readme.txt from the installer
- bpo-29326: Ignores blank lines in ._pth files (Patch by Alexey Izbyshev)
- bpo-28164: Correctly handle special console filenames (patch by Eryk Sun)
- bpo-29409: Implement PEP 529 for io.FileIO (Patch by Eryk Sun)
- bpo-29392: Prevent crash when passing invalid arguments into msvcrt module.
- bpo-25778: winreg does not truncate string correctly (Patch by Eryk Sun)
- bpo-28896: Deprecate WindowsRegistryFinder and disable it by default.

### C API

- bpo-27867: Function PySlice_GetIndicesEx() is replaced with a macro if Py_LIMITED_API is not set or set to the value between 0x03050400 and 0x03060000 (not including) or 0x03060100 or higher.
- bpo-29083: Fixed the declaration of some public API functions. PyArg_VaParse() and PyArg_VaParseTupleAndKeywords() were not available in limited API. PyArg_ValidateKeywordArguments(), PyArg_UnpackTuple() and Py_BuildValue() were not available in limited API of version < 3.3 when PY_SSIZE_T_CLEAN is defined.
- bpo-29058: All stable API extensions added after Python 3.2 are now available only when Py_LIMITED_API is set to the PY_VERSION_HEX value of the minimum Python version supporting this API.

### Documentation

- bpo-28929: Link the documentation to its source file on GitHub.
- bpo-25008: Document smtpd.py as effectively deprecated and add a pointer to aiosmtpd, a third-party asyncio-based replacement.
- bpo-26355: Add canonical header link on each page to corresponding major version of the documentation. Patch by Matthias Bussonnier.
- bpo-29349: Fix Python 2 syntax in code for building the documentation.

### Tests

- bpo-28087: Skip test_asyncore and test_eintr poll failures on macOS. Skip some tests of select.poll when running on macOS due to unresolved issues with the underlying system poll function on some macOS versions.
- bpo-29571: to match the behaviour of the `re.LOCALE` flag, test_re.test_locale_flag now uses `locale.getpreferredencoding(False)` to determine the candidate encoding for the test regex (allowing it to correctly skip the test when the default locale encoding is a multi-byte encoding)
- bpo-28950: Disallow -j0 to be combined with -T/-l in regrtest command line arguments.
- bpo-28683: Fix the tests that bind() a unix socket and raise PermissionError on Android for a non-root user.
- bpo-26939: Add the support.setswitchinterval() function to fix test_functools hanging on the Android armv7 qemu emulator.

### Build

- bpo-27593: sys.version and the platform module python_build(), python_branch(), and python_revision() functions now use git information rather than hg when building from a repo.
- bpo-29572: Update Windows build and OS X installers to use OpenSSL 1.0.2k.
- bpo-26851: Set Android compilation and link flags.
- bpo-28768: Fix implicit declaration of function _setmode. Patch by Masayuki Yamamoto
- bpo-29080: Removes hard dependency on hg.exe from PCBuild/build.bat
- bpo-23903: Added missed names to PC/python3.def.
- bpo-28762: lockf() is available on Android API level 24, but the F_LOCK macro is not defined in android-ndk-r13.
- bpo-28538: Fix the compilation error that occurs because if_nameindex() is available on Android API level 24, but the if_nameindex structure is not defined.
- bpo-20211: Do not add the directory for installing C header files and the directory for installing object code libraries to the cross compilation search paths. Original patch by Thomas Petazzoni.
- bpo-28849: Do not define sys.implementation._multiarch on Android.

## Python 3.6.0 final

Release date: 2016-12-23

No changes since release candidate 2

## Python 3.6.0 release candidate 2

Release date: 2016-12-16

### Core and Builtins

- bpo-28147: Fix a memory leak in split-table dictionaries: setattr() must not convert combined table into split table. Patch written by INADA Naoki.
- bpo-28990: Fix asyncio SSL hanging if connection is closed before handshake is completed. (Patch by HoHo-Ho)

### Tools/Demos

- bpo-28770: Fix python-gdb.py for fastcalls.

### Windows

- bpo-28896: Deprecate WindowsRegistryFinder.

### Build

- bpo-28898: Prevent gdb build errors due to HAVE_LONG_LONG redefinition.

## Python 3.6.0 release candidate 1

Release date: 2016-12-06

### Core and Builtins

- bpo-23722: Rather than silently producing a class that doesn’t support zero-argument `super()` in methods, failing to pass the new `__classcell__` namespace entry up to `type.__new__` now results in a `DeprecationWarning` and a class that supports zero-argument `super()`.
- bpo-28797: Modifying the class __dict__ inside the __set_name__ method of a descriptor that is used inside that class no longer prevents calling the __set_name__ method of other descriptors.
- bpo-28782: Fix a bug in the implementation `yield from` when checking if the next instruction is YIELD_FROM. Regression introduced by WORDCODE (bpo-26647).

### Library

- bpo-27030: Unknown escapes in re.sub() replacement template are allowed again. But they still are deprecated and will be disabled in 3.7.
- bpo-28835: Fix a regression introduced in warnings.catch_warnings(): call warnings.showwarning() if it was overriden inside the context manager.
- bpo-27172: To assist with upgrades from 2.7, the previously documented deprecation of `inspect.getfullargspec()` has been reversed. This decision may be revisited again after the Python 2.7 branch is no longer officially supported.
- bpo-26273: Add new `socket.TCP_CONGESTION` (Linux 2.6.13) and `socket.TCP_USER_TIMEOUT` (Linux 2.6.37) constants. Patch written by Omar Sandoval.
- bpo-24142: Reading a corrupt config file left configparser in an invalid state. Original patch by Florian Höch.
- bpo-28843: Fix asyncio C Task to handle exceptions __traceback__.

### C API

- bpo-28808: PyUnicode_CompareWithASCIIString() now never raises exceptions.

### Documentation

- bpo-23722: The data model reference and the porting section in the What’s New guide now cover the additional `__classcell__` handling needed for custom metaclasses to fully support PEP 487 and zero-argument `super()`.

### Tools/Demos

- bpo-28023: Fix python-gdb.py didn’t support new dict implementation.

## Python 3.6.0 beta 4

Release date: 2016-11-21

### Core and Builtins

- bpo-28532: Show sys.version when -V option is supplied twice.
- bpo-27100: The with-statement now checks for __enter__ before it checks for __exit__. This gives less confusing error messages when both methods are missing. Patch by Jonathan Ellington.
- bpo-28746: Fix the set_inheritable() file descriptor method on platforms that do not have the ioctl FIOCLEX and FIONCLEX commands.
- bpo-26920: Fix not getting the locale’s charset upon initializing the interpreter, on platforms that do not have langinfo.
- bpo-28648: Fixed crash in Py_DecodeLocale() in debug build on Mac OS X when decode astral characters. Patch by Xiang Zhang.
- bpo-19398: Extra slash no longer added to sys.path components in case of empty compile-time PYTHONPATH components.
- bpo-28665: Improve speed of the STORE_DEREF opcode by 40%.
- bpo-28583: PyDict_SetDefault didn’t combine split table when needed. Patch by Xiang Zhang.
- bpo-27243: Change PendingDeprecationWarning -> DeprecationWarning. As it was agreed in the issue, __aiter__ returning an awaitable should result in PendingDeprecationWarning in 3.5 and in DeprecationWarning in 3.6.
- bpo-26182: Fix a refleak in code that raises DeprecationWarning.
- bpo-28721: Fix asynchronous generators aclose() and athrow() to handle StopAsyncIteration propagation properly.

### Library

- bpo-28752: Restored the __reduce__() methods of datetime objects.
- bpo-28727: Regular expression patterns, _sre.SRE_Pattern objects created by re.compile(), become comparable (only x==y and x!=y operators). This change should fix the bpo-18383: don’t duplicate warning filters when the warnings module is reloaded (thing usually only done in unit tests).
- bpo-20572: The subprocess.Popen.wait method’s undocumented endtime parameter now raises a DeprecationWarning.
- bpo-25659: In ctypes, prevent a crash calling the from_buffer() and from_buffer_copy() methods on abstract classes like Array.
- bpo-19717: Makes Path.resolve() succeed on paths that do not exist. Patch by Vajrasky Kok
- bpo-28563: Fixed possible DoS and arbitrary code execution when handle plural form selections in the gettext module. The expression parser now supports exact syntax supported by GNU gettext.
- bpo-28387: Fixed possible crash in _io.TextIOWrapper deallocator when the garbage collector is invoked in other thread. Based on patch by Sebastian Cufre.
- bpo-28600: Optimize loop.call_soon.
- bpo-28613: Fix get_event_loop() return the current loop if called from coroutines/callbacks.
- bpo-28634: Fix asyncio.isfuture() to support unittest.Mock.
- bpo-26081: Fix refleak in _asyncio.Future.__iter__().throw.
- bpo-28639: Fix inspect.isawaitable to always return bool Patch by Justin Mayfield.
- bpo-28652: Make loop methods reject socket kinds they do not support.
- bpo-28653: Fix a refleak in functools.lru_cache.
- bpo-28703: Fix asyncio.iscoroutinefunction to handle Mock objects.
- bpo-28704: Fix create_unix_server to support Path-like objects (PEP 519).
- bpo-28720: Add collections.abc.AsyncGenerator.

### Documentation

- bpo-28513: Documented command-line interface of zipfile.

### Tests

- bpo-28666: Now test.support.rmtree is able to remove unwritable or unreadable directories.
- bpo-23839: Various caches now are cleared before running every test file.

### Build

- bpo-10656: Fix out-of-tree building on AIX. Patch by Tristan Carel and Michael Haubenwallner.
- bpo-26359: Rename –with-optimiations to –enable-optimizations.
- bpo-28676: Prevent missing ‘getentropy’ declaration warning on macOS. Patch by Gareth Rees.

## Python 3.6.0 beta 3

Release date: 2016-10-31

### Core and Builtins

- bpo-28128: Deprecation warning for invalid str and byte escape sequences now prints better information about where the error occurs. Patch by Serhiy Storchaka and Eric Smith.
- bpo-28509: dict.update() no longer allocate unnecessary large memory.
- bpo-28426: Fixed potential crash in PyUnicode_AsDecodedObject() in debug build.
- bpo-28517: Fixed of-by-one error in the peephole optimizer that caused keeping unreachable code.
- bpo-28214: Improved exception reporting for problematic __set_name__ attributes.
- bpo-23782: Fixed possible memory leak in _PyTraceback_Add() and exception loss in PyTraceBack_Here().
- bpo-28471: Fix “Python memory allocator called without holding the GIL” crash in socket.setblocking.

### Library

- bpo-27517: LZMA compressor and decompressor no longer raise exceptions if given empty data twice. Patch by Benjamin Fogle.
- bpo-28549: Fixed segfault in curses’s addch() with ncurses6.
- bpo-28449: tarfile.open() with mode “r” or “r:” now tries to open a tar file with compression before trying to open it without compression. Otherwise it had 50% chance failed with ignore_zeros=True.
- bpo-23262: The webbrowser module now supports Firefox 36+ and derived browsers. Based on patch by Oleg Broytman.
- bpo-27939: Fixed bugs in tkinter.ttk.LabeledScale and tkinter.Scale caused by representing the scale as float value internally in Tk. tkinter.IntVar now works if float value is set to underlying Tk variable.
- bpo-18844: The various ways of specifying weights for random.choices() now produce the same result sequences.
- bpo-28255: calendar.TextCalendar().prmonth() no longer prints a space at the start of new line after printing a month’s calendar. Patch by Xiang Zhang.
- bpo-20491: The textwrap.TextWrapper class now honors non-breaking spaces. Based on patch by Kaarle Ritvanen.
- bpo-28353: os.fwalk() no longer fails on broken links.
- bpo-28430: Fix iterator of C implemented asyncio.Future doesn’t accept non-None value is passed to it.send(val).
- bpo-27025: Generated names for Tkinter widgets now start by the “!” prefix for readability.
- bpo-25464: Fixed HList.header_exists() in tkinter.tix module by addin a workaround to Tix library bug.
- bpo-28488: shutil.make_archive() no longer adds entry “./” to ZIP archive.
- bpo-25953: re.sub() now raises an error for invalid numerical group reference in replacement template even if the pattern is not found in the string. Error message for invalid group reference now includes the group index and the position of the reference. Based on patch by SilentGhost.
- bpo-18219: Optimize csv.DictWriter for large number of columns. Patch by Mariatta Wijaya.
- bpo-28448: Fix C implemented asyncio.Future didn’t work on Windows.
- bpo-28480: Fix error building socket module when multithreading is disabled.
- bpo-24452: Make webbrowser support Chrome on Mac OS X.
- bpo-20766: Fix references leaked by pdb in the handling of SIGINT handlers.
- bpo-28492: Fix how StopIteration exception is raised in _asyncio.Future.
- bpo-28500: Fix asyncio to handle async gens GC from another thread.
- bpo-26923: Fix asyncio.Gather to refuse being cancelled once all children are done. Patch by Johannes Ebke.
- bpo-26796: Don’t configure the number of workers for default threadpool executor. Initial patch by Hans Lawrenz.
- bpo-28544: Implement asyncio.Task in C.

### Windows

- bpo-28522: Fixes mishandled buffer reallocation in getpathp.c

### Build

- bpo-28444: Fix missing extensions modules when cross compiling.
- bpo-28208: Update Windows build and OS X installers to use SQLite 3.14.2.
- bpo-28248: Update Windows build and OS X installers to use OpenSSL 1.0.2j.

### Tests

- bpo-26944: Fix test_posix for Android where ‘id -G’ is entirely wrong or missing the effective gid.
- bpo-28409: regrtest: fix the parser of command line arguments.

## Python 3.6.0 beta 2

Release date: 2016-10-10

### Core and Builtins

- bpo-28183: Optimize and cleanup dict iteration.
- bpo-26081: Added C implementation of asyncio.Future. Original patch by Yury Selivanov.
- bpo-28379: Added sanity checks and tests for PyUnicode_CopyCharacters(). Patch by Xiang Zhang.
- bpo-28376: The type of long range iterator is now registered as Iterator. Patch by Oren Milman.
- bpo-28376: Creating instances of range_iterator by calling range_iterator type now is deprecated. Patch by Oren Milman.
- bpo-28376: The constructor of range_iterator now checks that step is not 0. Patch by Oren Milman.
- bpo-26906: Resolving special methods of uninitialized type now causes implicit initialization of the type instead of a fail.
- bpo-18287: PyType_Ready() now checks that tp_name is not NULL. Original patch by Niklas Koep.
- bpo-24098: Fixed possible crash when AST is changed in process of compiling it.
- bpo-28201: Dict reduces possibility of 2nd conflict in hash table when hashes have same lower bits.
- bpo-28350: String constants with null character no longer interned.
- bpo-26617: Fix crash when GC runs during weakref callbacks.
- bpo-27942: String constants now interned recursively in tuples and frozensets.
- bpo-21578: Fixed misleading error message when ImportError called with invalid keyword args.
- bpo-28203: Fix incorrect type in complex(1.0, {2:3}) error message. Patch by Soumya Sharma.
- bpo-28086: Single var-positional argument of tuple subtype was passed unscathed to the C-defined function. Now it is converted to exact tuple.
- bpo-28214: Now __set_name__ is looked up on the class instead of the instance.
- bpo-27955: Fallback on reading /dev/urandom device when the getrandom() syscall fails with EPERM, for example when blocked by SECCOMP.
- bpo-28192: Don’t import readline in isolated mode.
- Upgrade internal unicode databases to Unicode version 9.0.0.
- bpo-28131: Fix a regression in zipimport’s compile_source(). zipimport should use the same optimization level as the interpreter.
- bpo-28126: Replace Py_MEMCPY with memcpy(). Visual Studio can properly optimize memcpy().
- bpo-28120: Fix dict.pop() for splitted dictionary when trying to remove a “pending key” (Not yet inserted in split-table). Patch by Xiang Zhang.
- bpo-26182: Raise DeprecationWarning when async and await keywords are used as variable/attribute/class/function name.

### Library

- bpo-27998: Fixed bytes path support in os.scandir() on Windows. Patch by Eryk Sun.

- bpo-28317: The disassembler now decodes FORMAT_VALUE argument.

- bpo-26293: Fixed writing ZIP files that starts not from the start of the file. Offsets in ZIP file now are relative to the start of the archive in conforming to the specification.

- bpo-28380: unittest.mock Mock autospec functions now properly support assert_called, assert_not_called, and assert_called_once.

- bpo-27181: remove statistics.geometric_mean and defer until 3.7.

- bpo-28229: lzma module now supports pathlib.

- bpo-28321: Fixed writing non-BMP characters with binary format in plistlib.

- bpo-28225: bz2 module now supports pathlib. Initial patch by Ethan Furman.

- bpo-28227: gzip now supports pathlib. Patch by Ethan Furman.

- bpo-27358: Optimized merging var-keyword arguments and improved error message when passing a non-mapping as a var-keyword argument.

- bpo-28257: Improved error message when passing a non-iterable as a var-positional argument. Added opcode BUILD_TUPLE_UNPACK_WITH_CALL.

- bpo-28322: Fixed possible crashes when unpickle itertools objects from incorrect pickle data. Based on patch by John Leitch.

- bpo-28228: imghdr now supports pathlib.

- bpo-28226: compileall now supports pathlib.

- bpo-28314: Fix function declaration (C flags) for the getiterator() method of xml.etree.ElementTree.Element.

- bpo-28148: Stop using localtime() and gmtime() in the time module.

  Introduced platform independent _PyTime_localtime API that is similar to POSIX localtime_r, but available on all platforms. Patch by Ed Schouten.

- bpo-28253: Fixed calendar functions for extreme months: 0001-01 and 9999-12.

  Methods itermonthdays() and itermonthdays2() are reimplemented so that they don’t call itermonthdates() which can cause datetime.date under/overflow.

- bpo-28275: Fixed possible use after free in the decompress() methods of the LZMADecompressor and BZ2Decompressor classes. Original patch by John Leitch.

- bpo-27897: Fixed possible crash in sqlite3.Connection.create_collation() if pass invalid string-like object as a name. Patch by Xiang Zhang.

- bpo-18844: random.choices() now has k as a keyword-only argument to improve the readability of common cases and come into line with the signature used in other languages.

- bpo-18893: Fix invalid exception handling in Lib/ctypes/macholib/dyld.py. Patch by Madison May.

- bpo-27611: Fixed support of default root window in the tkinter.tix module. Added the master parameter in the DisplayStyle constructor.

- bpo-27348: In the traceback module, restore the formatting of exception messages like “Exception: None”. This fixes a regression introduced in 3.5a2.

- bpo-25651: Allow falsy values to be used for msg parameter of subTest().

- bpo-27778: Fix a memory leak in os.getrandom() when the getrandom() is interrupted by a signal and a signal handler raises a Python exception.

- bpo-28200: Fix memory leak on Windows in the os module (fix path_converter() function).

- bpo-25400: RobotFileParser now correctly returns default values for crawl_delay and request_rate. Initial patch by Peter Wirtz.

- bpo-27932: Prevent memory leak in win32_ver().

- Fix UnboundLocalError in socket._sendfile_use_sendfile.

- bpo-28075: Check for ERROR_ACCESS_DENIED in Windows implementation of os.stat(). Patch by Eryk Sun.

- bpo-22493: Warning message emitted by using inline flags in the middle of regular expression now contains a (truncated) regex pattern. Patch by Tim Graham.

- bpo-25270: Prevent codecs.escape_encode() from raising SystemError when an empty bytestring is passed.

- bpo-28181: Get antigravity over HTTPS. Patch by Kaartic Sivaraam.

- bpo-25895: Enable WebSocket URL schemes in urllib.parse.urljoin. Patch by Gergely Imreh and Markus Holtermann.

- bpo-28114: Fix a crash in parse_envlist() when env contains byte strings. Patch by Eryk Sun.

- bpo-27599: Fixed buffer overrun in binascii.b2a_qp() and binascii.a2b_qp().

- bpo-27906: Fix socket accept exhaustion during high TCP traffic. Patch by Kevin Conway.

- bpo-28174: Handle when SO_REUSEPORT isn’t properly supported. Patch by Seth Michael Larson.

- bpo-26654: Inspect functools.partial in asyncio.Handle.__repr__. Patch by iceboy.

- bpo-26909: Fix slow pipes IO in asyncio. Patch by INADA Naoki.

- bpo-28176: Fix callbacks race in asyncio.SelectorLoop.sock_connect.

- bpo-27759: Fix selectors incorrectly retain invalid file descriptors. Patch by Mark Williams.

- bpo-28368: Refuse monitoring processes if the child watcher has no loop attached. Patch by Vincent Michel.

- bpo-28369: Raise RuntimeError when transport’s FD is used with add_reader, add_writer, etc.

- bpo-28370: Speedup asyncio.StreamReader.readexactly. Patch by Коренберг Марк.

- bpo-28371: Deprecate passing asyncio.Handles to run_in_executor.

- bpo-28372: Fix asyncio to support formatting of non-python coroutines.

- bpo-28399: Remove UNIX socket from FS before binding. Patch by Коренберг Марк.

- bpo-27972: Prohibit Tasks to await on themselves.

### Windows

- bpo-28402: Adds signed catalog files for stdlib on Windows.
- bpo-28333: Enables Unicode for ps1/ps2 and input() prompts. (Patch by Eryk Sun)
- bpo-28251: Improvements to help manuals on Windows.
- bpo-28110: launcher.msi has different product codes between 32-bit and 64-bit
- bpo-28161: Opening CON for write access fails
- bpo-28162: WindowsConsoleIO readall() fails if first line starts with Ctrl+Z
- bpo-28163: WindowsConsoleIO fileno() passes wrong flags to _open_osfhandle
- bpo-28164: _PyIO_get_console_type fails for various paths
- bpo-28137: Renames Windows path file to ._pth
- bpo-28138: Windows ._pth file should allow import site

### C API

- bpo-28426: Deprecated undocumented functions PyUnicode_AsEncodedObject(), PyUnicode_AsDecodedObject(), PyUnicode_AsDecodedUnicode() and PyUnicode_AsEncodedUnicode().

### Build

- bpo-28258: Fixed build with Estonian locale (python-config and distclean targets in Makefile). Patch by Arfrever Frehtes Taifersar Arahesis.
- bpo-26661: setup.py now detects system libffi with multiarch wrapper.
- bpo-15819: Remove redundant include search directory option for building outside the source tree.

### Tests

- bpo-28217: Adds _testconsole module to test console input.

## Python 3.6.0 beta 1

Release date: 2016-09-12

### Core and Builtins

- bpo-23722: The __class__ cell used by zero-argument super() is now initialized from type.__new__ rather than __build_class__, so class methods relying on that will now work correctly when called from metaclass methods during class creation. Patch by Martin Teichmann.
- bpo-25221: Fix corrupted result from PyLong_FromLong(0) when Python is compiled with NSMALLPOSINTS = 0.
- bpo-27080: Implement formatting support for PEP 515. Initial patch by Chris Angelico.
- bpo-27199: In tarfile, expose copyfileobj bufsize to improve throughput. Patch by Jason Fried.
- bpo-27948: In f-strings, only allow backslashes inside the braces (where the expressions are). This is a breaking change from the 3.6 alpha releases, where backslashes are allowed anywhere in an f-string. Also, require that expressions inside f-strings be enclosed within literal braces, and not escapes like `f'\x7b"hi"\x7d'`.
- bpo-28046: Remove platform-specific directories from sys.path.
- bpo-28071: Add early-out for differencing from an empty set.
- bpo-25758: Prevents zipimport from unnecessarily encoding a filename (patch by Eryk Sun)
- bpo-25856: The __module__ attribute of extension classes and functions now is interned. This leads to more compact pickle data with protocol 4.
- bpo-27213: Rework CALL_FUNCTION* opcodes to produce shorter and more efficient bytecode. Patch by Demur Rumed, design by Serhiy Storchaka, reviewed by Serhiy Storchaka and Victor Stinner.
- bpo-26331: Implement tokenizing support for PEP 515. Patch by Georg Brandl.
- bpo-27999: Make “global after use” a SyntaxError, and ditto for nonlocal. Patch by Ivan Levkivskyi.
- bpo-28003: Implement PEP 525 – Asynchronous Generators.
- bpo-27985: Implement PEP 526 – Syntax for Variable Annotations. Patch by Ivan Levkivskyi.
- bpo-26058: Add a new private version to the builtin dict type, incremented at each dictionary creation and at each dictionary change. Implementation of the PEP 509.
- bpo-27364: A backslash-character pair that is not a valid escape sequence now generates a DeprecationWarning. Patch by Emanuel Barry.
- bpo-27350: `dict` implementation is changed like PyPy. It is more compact and preserves insertion order. (Concept developed by Raymond Hettinger and patch by Inada Naoki.)
- bpo-27911: Remove unnecessary error checks in `exec_builtin_or_dynamic()`.
- bpo-27078: Added BUILD_STRING opcode. Optimized f-strings evaluation.
- bpo-17884: Python now requires systems with inttypes.h and stdint.h
- bpo-27961: Require platforms to support `long long`. Python hasn’t compiled without `long long` for years, so this is basically a formality.
- bpo-27355: Removed support for Windows CE. It was never finished, and Windows CE is no longer a relevant platform for Python.
- Implement PEP 523.
- bpo-27870: A left shift of zero by a large integer no longer attempts to allocate large amounts of memory.
- bpo-25402: In int-to-decimal-string conversion, improve the estimate of the intermediate memory required, and remove an unnecessarily strict overflow check. Patch by Serhiy Storchaka.
- bpo-27214: In long_invert, be more careful about modifying object returned by long_add, and remove an unnecessary check for small longs. Thanks Oren Milman for analysis and patch.
- bpo-27506: Support passing the bytes/bytearray.translate() “delete” argument by keyword.
- bpo-27812: Properly clear out a generator’s frame’s backreference to the generator to prevent crashes in frame.clear().
- bpo-27811: Fix a crash when a coroutine that has not been awaited is finalized with warnings-as-errors enabled.
- bpo-27587: Fix another issue found by PVS-Studio: Null pointer check after use of ‘def’ in _PyState_AddModule(). Initial patch by Christian Heimes.
- bpo-27792: The modulo operation applied to `bool` and other `int` subclasses now always returns an `int`. Previously the return type depended on the input values. Patch by Xiang Zhang.
- bpo-26984: int() now always returns an instance of exact int.
- bpo-25604: Fix a minor bug in integer true division; this bug could potentially have caused off-by-one-ulp results on platforms with unreliable ldexp implementations.
- bpo-24254: Make class definition namespace ordered by default.
- bpo-27662: Fix an overflow check in `List_New`: the original code was checking against `Py_SIZE_MAX` instead of the correct upper bound of `Py_SSIZE_T_MAX`. Patch by Xiang Zhang.
- bpo-27782: Multi-phase extension module import now correctly allows the `m_methods` field to be used to add module level functions to instances of non-module types returned from `Py_create_mod`. Patch by Xiang Zhang.
- bpo-27936: The round() function accepted a second None argument for some types but not for others. Fixed the inconsistency by accepting None for all numeric types.
- bpo-27487: Warn if a submodule argument to “python -m” or runpy.run_module() is found in sys.modules after parent packages are imported, but before the submodule is executed.
- bpo-27157: Make only type() itself accept the one-argument form. Patch by Eryk Sun and Emanuel Barry.
- bpo-27558: Fix a SystemError in the implementation of “raise” statement. In a brand new thread, raise a RuntimeError since there is no active exception to reraise. Patch written by Xiang Zhang.
- bpo-28008: Implement PEP 530 – asynchronous comprehensions.
- bpo-27942: Fix memory leak in codeobject.c

### Library

- bpo-28732: Fix crash in os.spawnv() with no elements in args
- bpo-28485: Always raise ValueError for negative compileall.compile_dir(workers=…) parameter, even when multithreading is unavailable.
- bpo-28037: Use sqlite3_get_autocommit() instead of setting Connection->inTransaction manually.
- bpo-25283: Attributes tm_gmtoff and tm_zone are now available on all platforms in the return values of time.localtime() and time.gmtime().
- bpo-24454: Regular expression match object groups are now accessible using __getitem__. “mo[x]” is equivalent to “mo.group(x)”.
- bpo-10740: sqlite3 no longer implicitly commit an open transaction before DDL statements.
- bpo-17941: Add a module parameter to collections.namedtuple().
- bpo-22493: Inline flags now should be used only at the start of the regular expression. Deprecation warning is emitted if uses them in the middle of the regular expression.
- bpo-26885: xmlrpc now supports unmarshalling additional data types used by Apache XML-RPC implementation for numerics and None.
- bpo-28070: Fixed parsing inline verbose flag in regular expressions.
- bpo-19500: Add client-side SSL session resumption to the ssl module.
- bpo-28022: Deprecate ssl-related arguments in favor of SSLContext. The deprecation include manual creation of SSLSocket and certfile/keyfile (or similar) in ftplib, httplib, imaplib, smtplib, poplib and urllib.
- bpo-28043: SSLContext has improved default settings: OP_NO_SSLv2, OP_NO_SSLv3, OP_NO_COMPRESSION, OP_CIPHER_SERVER_PREFERENCE, OP_SINGLE_DH_USE, OP_SINGLE_ECDH_USE and HIGH ciphers without MD5.
- bpo-24693: Changed some RuntimeError’s in the zipfile module to more appropriate types. Improved some error messages and debugging output.
- bpo-17909: `json.load` and `json.loads` now support binary input encoded as UTF-8, UTF-16 or UTF-32. Patch by Serhiy Storchaka.
- bpo-27137: the pure Python fallback implementation of `functools.partial` now matches the behaviour of its accelerated C counterpart for subclassing, pickling and text representation purposes. Patch by Emanuel Barry and Serhiy Storchaka.
- Fix possible integer overflows and crashes in the mmap module with unusual usage patterns.
- bpo-1703178: Fix the ability to pass the –link-objects option to the distutils build_ext command.
- bpo-28019: itertools.count() no longer rounds non-integer step in range between 1.0 and 2.0 to 1.
- bpo-18401: Pdb now supports the ‘readrc’ keyword argument to control whether .pdbrc files should be read. Patch by Martin Matusiak and Sam Kimbrel.
- bpo-25969: Update the lib2to3 grammar to handle the unpacking generalizations added in 3.5.
- bpo-14977: mailcap now respects the order of the lines in the mailcap files (“first match”), as required by RFC 1542. Patch by Michael Lazar.
- bpo-28082: Convert re flag constants to IntFlag.
- bpo-28025: Convert all ssl module constants to IntEnum and IntFlags. SSLContext properties now return flags and enums.
- bpo-23591: Add Flag, IntFlag, and auto() to enum module.
- bpo-433028: Added support of modifier spans in regular expressions.
- bpo-24594: Validates persist parameter when opening MSI database
- bpo-17582: xml.etree.ElementTree nows preserves whitespaces in attributes (Patch by Duane Griffin. Reviewed and approved by Stefan Behnel.)
- bpo-28047: Fixed calculation of line length used for the base64 CTE in the new email policies.
- bpo-27576: Fix call order in OrderedDict.__init__().
- email.generator.DecodedGenerator now supports the policy keyword.
- bpo-28027: Remove undocumented modules from `Lib/plat-*`: IN, CDROM, DLFCN, TYPES, CDIO, and STROPTS.
- bpo-27445: Don’t pass str(_charset) to MIMEText.set_payload(). Patch by Claude Paroz.
- bpo-24277: The new email API is no longer provisional, and the docs have been reorganized and rewritten to emphasize the new API.
- bpo-22450: urllib now includes an `Accept: */*` header among the default headers. This makes the results of REST API requests more consistent and predictable especially when proxy servers are involved.
- lib2to3.pgen3.driver.load_grammar() now creates a stable cache file between runs given the same Grammar.txt input regardless of the hash randomization setting.
- bpo-28005: Allow ImportErrors in encoding implementation to propagate.
- bpo-26667: Support path-like objects in importlib.util.
- bpo-27570: Avoid zero-length memcpy() etc calls with null source pointers in the “ctypes” and “array” modules.
- bpo-22233: Break email header lines only on the RFC specified CR and LF characters, not on arbitrary unicode line breaks. This also fixes a bug in HTTP header parsing.
- bpo-27331: The email.mime classes now all accept an optional policy keyword.
- bpo-27988: Fix email iter_attachments incorrect mutation of payload list.
- bpo-16113: Add SHA-3 and SHAKE support to hashlib module.
- Eliminate a tautological-pointer-compare warning in _scproxy.c.
- bpo-27776: The `os.urandom()` function does now block on Linux 3.17 and newer until the system urandom entropy pool is initialized to increase the security. This change is part of the PEP 524.
- bpo-27778: Expose the Linux `getrandom()` syscall as a new `os.getrandom()` function. This change is part of the PEP 524.
- bpo-27691: Fix ssl module’s parsing of GEN_RID subject alternative name fields in X.509 certs.
- bpo-18844: Add random.choices().
- bpo-25761: Improved error reporting about truncated pickle data in C implementation of unpickler. UnpicklingError is now raised instead of AttributeError and ValueError in some cases.
- bpo-26798: Add BLAKE2 (blake2b and blake2s) to hashlib.
- bpo-26032: Optimized globbing in pathlib by using os.scandir(); it is now about 1.5–4 times faster.
- bpo-25596: Optimized glob() and iglob() functions in the glob module; they are now about 3–6 times faster.
- bpo-27928: Add scrypt (password-based key derivation function) to hashlib module (requires OpenSSL 1.1.0).
- bpo-27850: Remove 3DES from ssl module’s default cipher list to counter measure sweet32 attack (CVE-2016-2183).
- bpo-27766: Add ChaCha20 Poly1305 to ssl module’s default cipher list. (Required OpenSSL 1.1.0 or LibreSSL).
- bpo-25387: Check return value of winsound.MessageBeep.
- bpo-27866: Add SSLContext.get_ciphers() method to get a list of all enabled ciphers.
- bpo-27744: Add AF_ALG (Linux Kernel crypto) to socket module.
- bpo-26470: Port ssl and hashlib module to OpenSSL 1.1.0.
- bpo-11620: Fix support for SND_MEMORY in winsound.PlaySound. Based on a patch by Tim Lesher.
- bpo-11734: Add support for IEEE 754 half-precision floats to the struct module. Based on a patch by Eli Stevens.
- bpo-27919: Deprecated `extra_path` distribution option in distutils packaging.
- bpo-23229: Add new `cmath` constants: `cmath.inf` and `cmath.nan` to match `math.inf` and `math.nan`, and also `cmath.infj` and `cmath.nanj` to match the format used by complex repr.
- bpo-27842: The csv.DictReader now returns rows of type OrderedDict. (Contributed by Steve Holden.)
- Remove support for passing a file descriptor to os.access. It never worked but previously didn’t raise.
- bpo-12885: Fix error when distutils encounters symlink.
- bpo-27881: Fixed possible bugs when setting sqlite3.Connection.isolation_level. Based on patch by Xiang Zhang.
- bpo-27861: Fixed a crash in sqlite3.Connection.cursor() when a factory creates not a cursor. Patch by Xiang Zhang.
- bpo-19884: Avoid spurious output on OS X with Gnu Readline.
- bpo-27706: Restore deterministic behavior of random.Random().seed() for string seeds using seeding version 1. Allows sequences of calls to random() to exactly match those obtained in Python 2. Patch by Nofar Schnider.
- bpo-10513: Fix a regression in Connection.commit(). Statements should not be reset after a commit.
- bpo-12319: Chunked transfer encoding support added to http.client.HTTPConnection requests. The urllib.request.AbstractHTTPHandler class does not enforce a Content-Length header any more. If a HTTP request has a file or iterable body, but no Content-Length header, the library now falls back to use chunked transfer-encoding.
- A new version of typing.py from https://github.com/python/typing: - Collection (only for 3.6) (bpo-27598) - Add FrozenSet to __all__ (upstream #261) - fix crash in _get_type_vars() (upstream #259) - Remove the dict constraint in ForwardRef._eval_type (upstream #252)
- bpo-27832: Make `_normalize` parameter to `Fraction` constuctor keyword-only, so that `Fraction(2, 3, 4)` now raises `TypeError`.
- bpo-27539: Fix unnormalised `Fraction.__pow__` result in the case of negative exponent and negative base.
- bpo-21718: cursor.description is now available for queries using CTEs.
- bpo-27819: In distutils sdists, simply produce the “gztar” (gzipped tar format) distributions on all platforms unless “formats” is supplied.
- bpo-2466: posixpath.ismount now correctly recognizes mount points which the user does not have permission to access.
- bpo-9998: On Linux, ctypes.util.find_library now looks in LD_LIBRARY_PATH for shared libraries.
- bpo-27573: exit message for code.interact is now configurable.
- bpo-27930: Improved behaviour of logging.handlers.QueueListener. Thanks to Paulo Andrade and Petr Viktorin for the analysis and patch.
- bpo-6766: Distributed reference counting added to multiprocessing to support nesting of shared values / proxy objects.
- bpo-21201: Improves readability of multiprocessing error message. Thanks to Wojciech Walczak for patch.
- asyncio: Add set_protocol / get_protocol to Transports.
- bpo-27456: asyncio: Set TCP_NODELAY by default.

### IDLE

- bpo-15308: Add ‘interrupt execution’ (^C) to Shell menu. Patch by Roger Serwy, updated by Bayard Randel.
- bpo-27922: Stop IDLE tests from ‘flashing’ gui widgets on the screen.
- bpo-27891: Consistently group and sort imports within idlelib modules.
- bpo-17642: add larger font sizes for classroom projection.
- Add version to title of IDLE help window.
- bpo-25564: In section on IDLE – console differences, mention that using exec means that __builtins__ is defined for each statement.
- bpo-27821: Fix 3.6.0a3 regression that prevented custom key sets from being selected when no custom theme was defined.

### C API

- bpo-26900: Excluded underscored names and other private API from limited API.
- bpo-26027: Add support for path-like objects in PyUnicode_FSConverter() & PyUnicode_FSDecoder().

### Tests

- bpo-27427: Additional tests for the math module. Patch by Francisco Couzo.
- bpo-27953: Skip math and cmath tests that fail on OS X 10.4 due to a poor libm implementation of tan.
- bpo-26040: Improve test_math and test_cmath coverage and rigour. Patch by Jeff Allen.
- bpo-27787: Call gc.collect() before checking each test for “dangling threads”, since the dangling threads are weak references.

### Build

- bpo-27566: Fix clean target in freeze makefile (patch by Lisa Roach)
- bpo-27705: Update message in validate_ucrtbase.py
- bpo-27976: Deprecate building _ctypes with the bundled copy of libffi on non-OSX UNIX platforms.
- bpo-27983: Cause lack of llvm-profdata tool when using clang as required for PGO linking to be a configure time error rather than make time when `--with-optimizations` is enabled. Also improve our ability to find the llvm-profdata tool on MacOS and some Linuxes.
- bpo-21590: Support for DTrace and SystemTap probes.
- bpo-26307: The profile-opt build now applies PGO to the built-in modules.
- bpo-26359: Add the –with-optimizations flag to turn on LTO and PGO build support when available.
- bpo-27917: Set platform triplets for Android builds.
- bpo-25825: Update references to the $(LIBPL) installation path on AIX. This path was changed in 3.2a4.
- Update OS X installer to use SQLite 3.14.1 and XZ 5.2.2.
- bpo-21122: Fix LTO builds on OS X.
- bpo-17128: Build OS X installer with a private copy of OpenSSL. Also provide a sample Install Certificates command script to install a set of root certificates from the third-party certifi module.

### Tools/Demos

- bpo-27952: Get Tools/scripts/fixcid.py working with Python 3 and the current “re” module, avoid invalid Python backslash escapes, and fix a bug parsing escaped C quote signs.

### Windows

- bpo-28065: Update xz dependency to 5.2.2 and build it from source.
- bpo-25144: Ensures TargetDir is set before continuing with custom install.
- bpo-1602: Windows console doesn’t input or print Unicode (PEP 528)
- bpo-27781: Change file system encoding on Windows to UTF-8 (PEP 529)
- bpo-27731: Opt-out of MAX_PATH on Windows 10
- bpo-6135: Adds encoding and errors parameters to subprocess.
- bpo-27959: Adds oem encoding, alias ansi to mbcs, move aliasmbcs to codec lookup.
- bpo-27982: The functions of the winsound module now accept keyword arguments.
- bpo-20366: Build full text search support into SQLite on Windows.
- bpo-27756: Adds new icons for Python files and processes on Windows. Designs by Cherry Wang.
- bpo-27883: Update sqlite to 3.14.1.0 on Windows.

## Python 3.6.0 alpha 4

Release date: 2016-08-15

### Core and Builtins

- bpo-27704: Optimized creating bytes and bytearray from byte-like objects and iterables. Speed up to 3 times for short objects. Original patch by Naoki Inada.
- bpo-26823: Large sections of repeated lines in tracebacks are now abbreviated as “[Previous line repeated {count} more times]” by the builtin traceback rendering. Patch by Emanuel Barry.
- bpo-27574: Decreased an overhead of parsing keyword arguments in functions implemented with using Argument Clinic.
- bpo-22557: Now importing already imported modules is up to 2.5 times faster.
- bpo-17596: Include <wincrypt.h> to help with Min GW building.
- bpo-17599: On Windows, rename the privately defined REPARSE_DATA_BUFFER structure to avoid conflicting with the definition from Min GW.
- bpo-27507: Add integer overflow check in bytearray.extend(). Patch by Xiang Zhang.
- bpo-27581: Don’t rely on wrapping for overflow check in PySequence_Tuple(). Patch by Xiang Zhang.
- bpo-1621: Avoid signed integer overflow in list and tuple operations. Patch by Xiang Zhang.
- bpo-27419: Standard __import__() no longer look up “__import__” in globals or builtins for importing submodules or “from import”. Fixed a crash if raise a warning about unabling to resolve package from __spec__ or __package__.
- bpo-27083: Respect the PYTHONCASEOK environment variable under Windows.
- bpo-27514: Make having too many statically nested blocks a SyntaxError instead of SystemError.
- bpo-27366: Implemented PEP 487 (Simpler customization of class creation). Upon subclassing, the __init_subclass__ classmethod is called on the base class. Descriptors are initialized with __set_name__ after class creation.

### Library

- bpo-26027: Add PEP 519/__fspath__() support to the os and os.path modules. Includes code from Jelle Zijlstra. (See also: bpo-27524)
- bpo-27598: Add Collections to collections.abc. Patch by Ivan Levkivskyi, docs by Neil Girdhar.
- bpo-25958: Support “anti-registration” of special methods from various ABCs, like __hash__, __iter__ or __len__. All these (and several more) can be set to None in an implementation class and the behavior will be as if the method is not defined at all. (Previously, this mechanism existed only for __hash__, to make mutable classes unhashable.) Code contributed by Andrew Barnert and Ivan Levkivskyi.
- bpo-16764: Support keyword arguments to zlib.decompress(). Patch by Xiang Zhang.
- bpo-27736: Prevent segfault after interpreter re-initialization due to ref count problem introduced in code for bpo-27038 in 3.6.0a3. Patch by Xiang Zhang.
- bpo-25628: The verbose and rename parameters for collections.namedtuple are now keyword-only.
- bpo-12345: Add mathematical constant tau to math and cmath. See also PEP 628.
- bpo-26823: traceback.StackSummary.format now abbreviates large sections of repeated lines as “[Previous line repeated {count} more times]” (this change then further affects other traceback display operations in the module). Patch by Emanuel Barry.
- bpo-27664: Add to concurrent.futures.thread.ThreadPoolExecutor() the ability to specify a thread name prefix.
- bpo-27181: Add geometric_mean and harmonic_mean to statistics module.
- bpo-27573: code.interact now prints an message when exiting.
- bpo-6422: Add autorange method to timeit.Timer objects.
- bpo-27773: Correct some memory management errors server_hostname in _ssl.wrap_socket().
- bpo-26750: unittest.mock.create_autospec() now works properly for subclasses of property() and other data descriptors. Removes the never publicly used, never documented unittest.mock.DescriptorTypes tuple.
- bpo-26754: Undocumented support of general bytes-like objects as path in compile() and similar functions is now deprecated.
- bpo-26800: Undocumented support of general bytes-like objects as paths in os functions is now deprecated.
- bpo-26981: Add _order_ compatibility shim to enum.Enum for Python 2/3 code bases.
- bpo-27661: Added tzinfo keyword argument to datetime.combine.
- In the curses module, raise an error if window.getstr() or window.instr() is passed a negative value.
- bpo-27783: Fix possible usage of uninitialized memory in operator.methodcaller.
- bpo-27774: Fix possible Py_DECREF on unowned object in _sre.
- bpo-27760: Fix possible integer overflow in binascii.b2a_qp.
- bpo-27758: Fix possible integer overflow in the _csv module for large record lengths.
- bpo-27568: Prevent HTTPoxy attack (CVE-2016-1000110). Ignore the HTTP_PROXY variable when REQUEST_METHOD environment is set, which indicates that the script is in CGI mode.
- bpo-7063: Remove dead code from the “array” module’s slice handling. Patch by Chuck.
- bpo-27656: Do not assume sched.h defines any SCHED_* constants.
- bpo-27130: In the “zlib” module, fix handling of large buffers (typically 4 GiB) when compressing and decompressing. Previously, inputs were limited to 4 GiB, and compression and decompression operations did not properly handle results of 4 GiB.
- bpo-24773: Implemented PEP 495 (Local Time Disambiguation).
- Expose the EPOLLEXCLUSIVE constant (when it is defined) in the select module.
- bpo-27567: Expose the EPOLLRDHUP and POLLRDHUP constants in the select module.
- bpo-1621: Avoid signed int negation overflow in the “audioop” module.
- bpo-27533: Release GIL in nt._isdir
- bpo-17711: Fixed unpickling by the persistent ID with protocol 0. Original patch by Alexandre Vassalotti.
- bpo-27522: Avoid an unintentional reference cycle in email.feedparser.
- bpo-27512: Fix a segfault when os.fspath() called an __fspath__() method that raised an exception. Patch by Xiang Zhang.

### IDLE

- bpo-27714: text_textview and test_autocomplete now pass when re-run in the same process. This occurs when test_idle fails when run with the -w option but without -jn. Fix warning from test_config.
- bpo-27621: Put query response validation error messages in the query box itself instead of in a separate messagebox. Redo tests to match. Add Mac OSX refinements. Original patch by Mark Roseman.
- bpo-27620: Escape key now closes Query box as cancelled.
- bpo-27609: IDLE: tab after initial whitespace should tab, not autocomplete. This fixes problem with writing docstrings at least twice indented.
- bpo-27609: Explicitly return None when there are also non-None returns. In a few cases, reverse a condition and eliminate a return.
- bpo-25507: IDLE no longer runs buggy code because of its tkinter imports. Users must include the same imports required to run directly in Python.
- bpo-27173: Add ‘IDLE Modern Unix’ to the built-in key sets. Make the default key set depend on the platform. Add tests for the changes to the config module.
- bpo-27452: add line counter and crc to IDLE configHandler test dump.

### Tests

- bpo-25805: Skip a test in test_pkgutil as needed that doesn’t work when `__name__ == __main__`. Patch by SilentGhost.
- bpo-27472: Add test.support.unix_shell as the path to the default shell.
- bpo-27369: In test_pyexpat, avoid testing an error message detail that changed in Expat 2.2.0.
- bpo-27594: Prevent assertion error when running test_ast with coverage enabled: ensure code object has a valid first line number. Patch suggested by Ivan Levkivskyi.

### Windows

- bpo-27647: Update bundled Tcl/Tk to 8.6.6.
- bpo-27610: Adds PEP 514 metadata to Windows installer
- bpo-27469: Adds a shell extension to the launcher so that drag and drop works correctly.
- bpo-27309: Enables proper Windows styles in python[w].exe manifest.

### Build

- bpo-27713: Suppress spurious build warnings when updating importlib’s bootstrap files. Patch by Xiang Zhang
- bpo-25825: Correct the references to Modules/python.exp, which is required on AIX. The references were accidentally changed in 3.5.0a1.
- bpo-27453: CPP invocation in configure must use CPPFLAGS. Patch by Chi Hsuan Yen.
- bpo-27641: The configure script now inserts comments into the makefile to prevent the pgen and _freeze_importlib executables from being cross-compiled.
- bpo-26662: Set PYTHON_FOR_GEN in configure as the Python program to be used for file generation during the build.
- bpo-10910: Avoid C++ compilation errors on FreeBSD and OS X. Also update FreedBSD version checks for the original ctype UTF-8 workaround.

## Python 3.6.0 alpha 3

Release date: 2016-07-11

### Core and Builtins

- bpo-27473: Fixed possible integer overflow in bytes and bytearray concatenations. Patch by Xiang Zhang.
- bpo-23034: The output of a special Python build with defined COUNT_ALLOCS, SHOW_ALLOC_COUNT or SHOW_TRACK_COUNT macros is now off by default. It can be re-enabled using the “-X showalloccount” option. It now outputs to stderr instead of stdout.
- bpo-27443: __length_hint__() of bytearray iterators no longer return a negative integer for a resized bytearray.
- bpo-27007: The fromhex() class methods of bytes and bytearray subclasses now return an instance of corresponding subclass.

### Library

- bpo-26844: Fix error message for imp.find_module() to refer to ‘path’ instead of ‘name’. Patch by Lev Maximov.
- bpo-23804: Fix SSL zero-length recv() calls to not block and not raise an error about unclean EOF.
- bpo-27466: Change time format returned by http.cookie.time2netscape, confirming the netscape cookie format and making it consistent with documentation.
- bpo-21708: Deprecated dbm.dumb behavior that differs from common dbm behavior: creating a database in ‘r’ and ‘w’ modes and modifying a database in ‘r’ mode.
- bpo-26721: Change the socketserver.StreamRequestHandler.wfile attribute to implement BufferedIOBase. In particular, the write() method no longer does partial writes.
- bpo-22115: Added methods trace_add, trace_remove and trace_info in the tkinter.Variable class. They replace old methods trace_variable, trace, trace_vdelete and trace_vinfo that use obsolete Tcl commands and might not work in future versions of Tcl. Fixed old tracing methods: trace_vdelete() with wrong mode no longer break tracing, trace_vinfo() now always returns a list of pairs of strings, tracing in the “u” mode now works.
- bpo-26243: Only the level argument to zlib.compress() is keyword argument now. The first argument is positional-only.
- bpo-27038: Expose the DirEntry type as os.DirEntry. Code patch by Jelle Zijlstra.
- bpo-27186: Update os.fspath()/PyOS_FSPath() to check the return value of __fspath__() to be either str or bytes.
- bpo-18726: All optional parameters of the dump(), dumps(), load() and loads() functions and JSONEncoder and JSONDecoder class constructors in the json module are now keyword-only.
- bpo-27319: Methods selection_set(), selection_add(), selection_remove() and selection_toggle() of ttk.TreeView now allow passing multiple items as multiple arguments instead of passing them as a tuple. Deprecated undocumented ability of calling the selection() method with arguments.
- bpo-27079: Fixed curses.ascii functions isblank(), iscntrl() and ispunct().
- bpo-27294: Numerical state in the repr for Tkinter event objects is now represented as a combination of known flags.
- bpo-27177: Match objects in the re module now support index-like objects as group indices. Based on patches by Jeroen Demeyer and Xiang Zhang.
- bpo-26754: Some functions (compile() etc) accepted a filename argument encoded as an iterable of integers. Now only strings and byte-like objects are accepted.
- bpo-26536: socket.ioctl now supports SIO_LOOPBACK_FAST_PATH. Patch by Daniel Stokes.
- bpo-27048: Prevents distutils failing on Windows when environment variables contain non-ASCII characters
- bpo-27330: Fixed possible leaks in the ctypes module.
- bpo-27238: Got rid of bare excepts in the turtle module. Original patch by Jelle Zijlstra.
- bpo-27122: When an exception is raised within the context being managed by a contextlib.ExitStack() and one of the exit stack generators catches and raises it in a chain, do not re-raise the original exception when exiting, let the new chained one through. This avoids the PEP 479 bug described in issue25782.

### Security

- bpo-27278: Fix os.urandom() implementation using getrandom() on Linux. Truncate size to INT_MAX and loop until we collected enough random bytes, instead of casting a directly Py_ssize_t to int.

### Library

- bpo-16864: sqlite3.Cursor.lastrowid now supports REPLACE statement. Initial patch by Alex LordThorsen.
- bpo-26386: Fixed ttk.TreeView selection operations with item id’s containing spaces.
- bpo-8637: Honor a pager set by the env var MANPAGER (in preference to one set by the env var PAGER).

### Security

- bpo-22636: Avoid shell injection problems with ctypes.util.find_library().

### Library

- bpo-16182: Fix various functions in the “readline” module to use the locale encoding, and fix get_begidx() and get_endidx() to return code point indexes.
- bpo-27392: Add loop.connect_accepted_socket(). Patch by Jim Fulton.

### IDLE

- bpo-27477: IDLE search dialogs now use ttk widgets.
- bpo-27173: Add ‘IDLE Modern Unix’ to the built-in key sets. Make the default key set depend on the platform. Add tests for the changes to the config module.
- bpo-27452: make command line “idle-test> python test_help.py” work. __file__ is relative when python is started in the file’s directory.
- bpo-27452: add line counter and crc to IDLE configHandler test dump.
- bpo-27380: IDLE: add query.py with base Query dialog and ttk widgets. Module had subclasses SectionName, ModuleName, and HelpSource, which are used to get information from users by configdialog and file =>Load Module. Each subclass has itw own validity checks. Using ModuleName allows users to edit bad module names instead of starting over. Add tests and delete the two files combined into the new one.
- bpo-27372: Test_idle no longer changes the locale.
- bpo-27365: Allow non-ascii chars in IDLE NEWS.txt, for contributor names.
- bpo-27245: IDLE: Cleanly delete custom themes and key bindings. Previously, when IDLE was started from a console or by import, a cascade of warnings was emitted. Patch by Serhiy Storchaka.
- bpo-24137: Run IDLE, test_idle, and htest with tkinter default root disabled. Fix code and tests that fail with this restriction. Fix htests to not create a second and redundant root and mainloop.
- bpo-27310: Fix IDLE.app failure to launch on OS X due to vestigial import.

### C API

- bpo-26754: PyUnicode_FSDecoder() accepted a filename argument encoded as an iterable of integers. Now only strings and byte-like objects are accepted.

### Build

- bpo-28066: Fix the logic that searches build directories for generated include files when building outside the source tree.
- bpo-27442: Expose the Android API level that python was built against, in sysconfig.get_config_vars() as ‘ANDROID_API_LEVEL’.
- bpo-27434: The interpreter that runs the cross-build, found in PATH, must now be of the same feature version (e.g. 3.6) as the source being built.
- bpo-26930: Update Windows builds to use OpenSSL 1.0.2h.
- bpo-23968: Rename the platform directory from plat-$(MACHDEP) to plat-$(PLATFORM_TRIPLET). Rename the config directory (LIBPL) from config-$(LDVERSION) to config-$(LDVERSION)-$(PLATFORM_TRIPLET). Install the platform specific _sysconfigdata module into the platform directory and rename it to include the ABIFLAGS.
- Don’t use largefile support for GNU/Hurd.

### Tools/Demos

- bpo-27332: Fixed the type of the first argument of module-level functions generated by Argument Clinic. Patch by Petr Viktorin.
- bpo-27418: Fixed Tools/importbench/importbench.py.

### Documentation

- bpo-19489: Moved the search box from the sidebar to the header and footer of each page. Patch by Ammar Askar.
- bpo-27285: Update documentation to reflect the deprecation of `pyvenv` and normalize on the term “virtual environment”. Patch by Steve Piercy.

### Tests

- bpo-27027: Added test.support.is_android that is True when this is an Android build.

## Python 3.6.0 alpha 2

Release date: 2016-06-13

### Core and Builtins

- bpo-27095: Simplified MAKE_FUNCTION and removed MAKE_CLOSURE opcodes. Patch by Demur Rumed.
- bpo-27190: Raise NotSupportedError if sqlite3 is older than 3.3.1. Patch by Dave Sawyer.
- bpo-27286: Fixed compiling BUILD_MAP_UNPACK_WITH_CALL opcode. Calling function with generalized unpacking (PEP 448) and conflicting keyword names could cause undefined behavior.
- bpo-27140: Added BUILD_CONST_KEY_MAP opcode.
- bpo-27186: Add support for os.PathLike objects to open() (part of PEP 519).
- bpo-27066: Fixed SystemError if a custom opener (for open()) returns a negative number without setting an exception.
- bpo-26983: float() now always return an instance of exact float. The deprecation warning is emitted if __float__ returns an instance of a strict subclass of float. In a future versions of Python this can be an error.
- bpo-27097: Python interpreter is now about 7% faster due to optimized instruction decoding. Based on patch by Demur Rumed.
- bpo-26647: Python interpreter now uses 16-bit wordcode instead of bytecode. Patch by Demur Rumed.
- bpo-23275: Allow assigning to an empty target list in round brackets: () = iterable.
- bpo-27243: Update the __aiter__ protocol: instead of returning an awaitable that resolves to an asynchronous iterator, the asynchronous iterator should be returned directly. Doing the former will trigger a PendingDeprecationWarning.

### Library

- Comment out socket (SO_REUSEPORT) and posix (O_SHLOCK, O_EXLOCK) constants exposed on the API which are not implemented on GNU/Hurd. They would not work at runtime anyway.
- bpo-27025: Generated names for Tkinter widgets are now more meaningful and recognizable.
- bpo-25455: Fixed crashes in repr of recursive ElementTree.Element and functools.partial objects.
- bpo-27294: Improved repr for Tkinter event objects.
- bpo-20508: Improve exception message of IPv{4,6}Network.__getitem__. Patch by Gareth Rees.

### Security

- bpo-26556: Update expat to 2.1.1, fixes CVE-2015-1283.
- Fix TLS stripping vulnerability in smtplib, CVE-2016-0772. Reported by Team Oststrom.

### Library

- bpo-21386: Implement missing IPv4Address.is_global property. It was documented since 07a5610bae9d. Initial patch by Roger Luethi.
- bpo-27029: Removed deprecated support of universal newlines mode from ZipFile.open().
- bpo-27030: Unknown escapes consisting of `'\'` and an ASCII letter in regular expressions now are errors. The re.LOCALE flag now can be used only with bytes patterns.
- bpo-27186: Add os.PathLike support to DirEntry (part of PEP 519). Initial patch by Jelle Zijlstra.
- bpo-20900: distutils register command now decodes HTTP responses correctly. Initial patch by ingrid.
- bpo-27186: Add os.PathLike support to pathlib, removing its provisional status (part of PEP 519). Initial patch by Dusty Phillips.
- bpo-27186: Add support for os.PathLike objects to os.fsencode() and os.fsdecode() (part of PEP 519).
- bpo-27186: Introduce os.PathLike and os.fspath() (part of PEP 519).
- A new version of typing.py provides several new classes and features: @overload outside stubs, Reversible, DefaultDict, Text, ContextManager, Type[], NewType(), TYPE_CHECKING, and numerous bug fixes (note that some of the new features are not yet implemented in mypy or other static analyzers). Also classes for PEP 492 (Awaitable, AsyncIterable, AsyncIterator) have been added (in fact they made it into 3.5.1 but were never mentioned).
- bpo-25738: Stop http.server.BaseHTTPRequestHandler.send_error() from sending a message body for 205 Reset Content. Also, don’t send Content header fields in responses that don’t have a body. Patch by Susumu Koshiba.
- bpo-21313: Fix the “platform” module to tolerate when sys.version contains truncated build information.

### Security

- bpo-26839: On Linux, `os.urandom()` now calls `getrandom()` with `GRND_NONBLOCK` to fall back on reading `/dev/urandom` if the urandom entropy pool is not initialized yet. Patch written by Colm Buckley.

### Library

- bpo-23883: Added missing APIs to __all__ to match the documented APIs for the following modules: cgi, mailbox, mimetypes, plistlib and smtpd. Patches by Jacek Kołodziej.
- bpo-27164: In the zlib module, allow decompressing raw Deflate streams with a predefined zdict. Based on patch by Xiang Zhang.
- bpo-24291: Fix wsgiref.simple_server.WSGIRequestHandler to completely write data to the client. Previously it could do partial writes and truncate data. Also, wsgiref.handler.ServerHandler can now handle stdout doing partial writes, but this is deprecated.
- bpo-21272: Use _sysconfigdata.py to initialize distutils.sysconfig.
- bpo-19611: `inspect` now reports the implicit `.0` parameters generated by the compiler for comprehension and generator expression scopes as if they were positional-only parameters called `implicit0`. Patch by Jelle Zijlstra.
- bpo-26809: Add `__all__` to `string`. Patch by Emanuel Barry.
- bpo-26373: subprocess.Popen.communicate now correctly ignores BrokenPipeError when the child process dies before .communicate() is called in more/all circumstances.
- signal, socket, and ssl module IntEnum constant name lookups now return a consistent name for values having multiple names. Ex: signal.Signals(6) now refers to itself as signal.SIGALRM rather than flipping between that and signal.SIGIOT based on the interpreter’s hash randomization seed.
- bpo-27167: Clarify the subprocess.CalledProcessError error message text when the child process died due to a signal.
- bpo-25931: Don’t define socketserver.Forking* names on platforms such as Windows that do not support os.fork().
- bpo-21776: distutils.upload now correctly handles HTTPError. Initial patch by Claudiu Popa.
- bpo-26526: Replace custom parse tree validation in the parser module with a simple DFA validator.
- bpo-27114: Fix SSLContext._load_windows_store_certs fails with PermissionError
- bpo-18383: Avoid creating duplicate filters when using filterwarnings and simplefilter. Based on patch by Alex Shkop.
- bpo-23026: winreg.QueryValueEx() now return an integer for REG_QWORD type.
- bpo-26741: subprocess.Popen destructor now emits a ResourceWarning warning if the child process is still running.
- bpo-27056: Optimize pickle.load() and pickle.loads(), up to 10% faster to deserialize a lot of small objects.
- bpo-21271: New keyword only parameters in reset_mock call.

### IDLE

- bpo-5124: Paste with text selected now replaces the selection on X11. This matches how paste works on Windows, Mac, most modern Linux apps, and ttk widgets. Original patch by Serhiy Storchaka.
- bpo-24750: Switch all scrollbars in IDLE to ttk versions. Where needed, minimal tests are added to cover changes.
- bpo-24759: IDLE requires tk 8.5 and availability ttk widgets. Delete now unneeded tk version tests and code for older versions. Add test for IDLE syntax colorizer.
- bpo-27239: idlelib.macosx.isXyzTk functions initialize as needed.
- bpo-27262: move Aqua unbinding code, which enable context menus, to macosx.
- bpo-24759: Make clear in idlelib.idle_test.__init__ that the directory is a private implementation of test.test_idle and tool for maintainers.
- bpo-27196: Stop ‘ThemeChanged’ warnings when running IDLE tests. These persisted after other warnings were suppressed in #20567. Apply Serhiy Storchaka’s update_idletasks solution to four test files. Record this additional advice in idle_test/README.txt
- bpo-20567: Revise idle_test/README.txt with advice about avoiding tk warning messages from tests. Apply advice to several IDLE tests.
- bpo-24225: Update idlelib/README.txt with new file names and event handlers.
- bpo-27156: Remove obsolete code not used by IDLE.
- bpo-27117: Make colorizer htest and turtledemo work with dark themes. Move code for configuring text widget colors to a new function.
- bpo-24225: Rename many `idlelib/*.py` and `idle_test/test_*.py` files. Edit files to replace old names with new names when the old name referred to the module rather than the class it contained. See the issue and IDLE section in What’s New in 3.6 for more.
- bpo-26673: When tk reports font size as 0, change to size 10. Such fonts on Linux prevented the configuration dialog from opening.
- bpo-21939: Add test for IDLE’s percolator. Original patch by Saimadhav Heblikar.
- bpo-21676: Add test for IDLE’s replace dialog. Original patch by Saimadhav Heblikar.
- bpo-18410: Add test for IDLE’s search dialog. Original patch by Westley Martínez.
- bpo-21703: Add test for undo delegator. Patch mostly by Saimadhav Heblikar .
- bpo-27044: Add ConfigDialog.remove_var_callbacks to stop memory leaks.
- bpo-23977: Add more asserts to test_delegator.

### Documentation

- bpo-16484: Change the default PYTHONDOCS URL to “https:”, and fix the resulting links to use lowercase. Patch by Sean Rodman, test by Kaushik Nadikuditi.
- bpo-24136: Document the new PEP 448 unpacking syntax of 3.5.
- bpo-22558: Add remaining doc links to source code for Python-coded modules. Patch by Yoni Lavi.

### Tests

- bpo-25285: regrtest now uses subprocesses when the -j1 command line option is used: each test file runs in a fresh child process. Before, the -j1 option was ignored.
- bpo-25285: Tools/buildbot/test.bat script now uses -j1 by default to run each test file in fresh child process.

### Windows

- bpo-27064: The py.exe launcher now defaults to Python 3. The Windows launcher `py.exe` no longer prefers an installed Python 2 version over Python 3 by default when used interactively.

### Build

- bpo-27229: Fix the cross-compiling pgen rule for in-tree builds. Patch by Xavier de Gaye.
- bpo-26930: Update OS X 10.5+ 32-bit-only installer to build and link with OpenSSL 1.0.2h.

### Windows

- bpo-17500: Remove unused and outdated icons. (See also: https://github.com/python/pythondotorg/issues/945)

### C API

- bpo-27186: Add the PyOS_FSPath() function (part of PEP 519).
- bpo-26282: PyArg_ParseTupleAndKeywords() now supports positional-only parameters.

### Tools/Demos

- bpo-26282: Argument Clinic now supports positional-only and keyword parameters in the same function.

## Python 3.6.0 alpha 1

Release date: 2016-05-16

### Core and Builtins

- bpo-20041: Fixed TypeError when frame.f_trace is set to None. Patch by Xavier de Gaye.
- bpo-26168: Fixed possible refleaks in failing Py_BuildValue() with the “N” format unit.
- bpo-26991: Fix possible refleak when creating a function with annotations.
- bpo-27039: Fixed bytearray.remove() for values greater than 127. Based on patch by Joe Jevnik.
- bpo-23640: int.from_bytes() no longer bypasses constructors for subclasses.
- bpo-27005: Optimized the float.fromhex() class method for exact float. It is now 2 times faster.
- bpo-18531: Single var-keyword argument of dict subtype was passed unscathed to the C-defined function. Now it is converted to exact dict.
- bpo-26811: gc.get_objects() no longer contains a broken tuple with NULL pointer.
- bpo-20120: Use RawConfigParser for .pypirc parsing, removing support for interpolation unintentionally added with move to Python 3. Behavior no longer does any interpolation in .pypirc files, matching behavior in Python 2.7 and Setuptools 19.0.
- bpo-26249: Memory functions of the `PyMem_Malloc()` domain (`PYMEM_DOMAIN_MEM`) now use the pymalloc allocator rather than system `malloc()`. Applications calling `PyMem_Malloc()` without holding the GIL can now crash: use `PYTHONMALLOC=debug` environment variable to validate the usage of memory allocators in your application.
- bpo-26802: Optimize function calls only using unpacking like `func(*tuple)` (no other positional argument, no keyword): avoid copying the tuple. Patch written by Joe Jevnik.
- bpo-26659: Make the builtin slice type support cycle collection.
- bpo-26718: super.__init__ no longer leaks memory if called multiple times. NOTE: A direct call of super.__init__ is not endorsed!
- bpo-27138: Fix the doc comment for FileFinder.find_spec().
- bpo-27147: Mention PEP 420 in the importlib docs.
- bpo-25339: PYTHONIOENCODING now has priority over locale in setting the error handler for stdin and stdout.
- bpo-26494: Fixed crash on iterating exhausting iterators. Affected classes are generic sequence iterators, iterators of str, bytes, bytearray, list, tuple, set, frozenset, dict, OrderedDict, corresponding views and os.scandir() iterator.
- bpo-26574: Optimize `bytes.replace(b'', b'.')` and `bytearray.replace(b'', b'.')`. Patch written by Josh Snider.
- bpo-26581: If coding cookie is specified multiple times on a line in Python source code file, only the first one is taken to account.
- bpo-19711: Add tests for reloading namespace packages.
- bpo-21099: Switch applicable importlib tests to use PEP 451 API.
- bpo-26563: Debug hooks on Python memory allocators now raise a fatal error if functions of the `PyMem_Malloc()` family are called without holding the GIL.
- bpo-26564: On error, the debug hooks on Python memory allocators now use the `tracemalloc` module to get the traceback where a memory block was allocated.
- bpo-26558: The debug hooks on Python memory allocator `PyObject_Malloc()` now detect when functions are called without holding the GIL.
- bpo-26516: Add `PYTHONMALLOC` environment variable to set the Python memory allocators and/or install debug hooks.
- bpo-26516: The `PyMem_SetupDebugHooks()` function can now also be used on Python compiled in release mode.
- bpo-26516: The `PYTHONMALLOCSTATS` environment variable can now also be used on Python compiled in release mode. It now has no effect if set to an empty string.
- bpo-26516: In debug mode, debug hooks are now also installed on Python memory allocators when Python is configured without pymalloc.
- bpo-26464: Fix str.translate() when string is ASCII and first replacements removes character, but next replacement uses a non-ASCII character or a string longer than 1 character. Regression introduced in Python 3.5.0.
- bpo-22836: Ensure exception reports from PyErr_Display() and PyErr_WriteUnraisable() are sensible even when formatting them produces secondary errors. This affects the reports produced by sys.__excepthook__() and when __del__() raises an exception.
- bpo-26302: Correct behavior to reject comma as a legal character for cookie names.
- bpo-26136: Upgrade the warning when a generator raises StopIteration from PendingDeprecationWarning to DeprecationWarning. Patch by Anish Shah.
- bpo-26204: The compiler now ignores all constant statements: bytes, str, int, float, complex, name constants (None, False, True), Ellipsis and ast.Constant; not only str and int. For example, `1.0` is now ignored in `def f(): 1.0`.
- bpo-4806: Avoid masking the original TypeError exception when using star (`*`) unpacking in function calls. Based on patch by Hagen Fürstenau and Daniel Urban.
- bpo-26146: Add a new kind of AST node: `ast.Constant`. It can be used by external AST optimizers, but the compiler does not emit directly such node.
- bpo-23601: Sped-up allocation of dict key objects by using Python’s small object allocator. (Contributed by Julian Taylor.)
- bpo-18018: Import raises ImportError instead of SystemError if a relative import is attempted without a known parent package.
- bpo-25843: When compiling code, don’t merge constants if they are equal but have a different types. For example, `f1, f2 = lambda: 1, lambda: 1.0` is now correctly compiled to two different functions: `f1()` returns `1` (`int`) and `f2()` returns `1.0` (`float`), even if `1` and `1.0` are equal.
- bpo-26107: The format of the `co_lnotab` attribute of code objects changes to support negative line number delta.
- bpo-26154: Add a new private _PyThreadState_UncheckedGet() function to get the current Python thread state, but don’t issue a fatal error if it is NULL. This new function must be used instead of accessing directly the _PyThreadState_Current variable. The variable is no more exposed since Python 3.5.1 to hide the exact implementation of atomic C types, to avoid compiler issues.
- bpo-25791: If __package__ != __spec__.parent or if neither __package__ or __spec__ are defined then ImportWarning is raised.
- bpo-22995: [UPDATE] Comment out the one of the pickleability tests in _PyObject_GetState() due to regressions observed in Cython-based projects.
- bpo-25961: Disallowed null characters in the type name.
- bpo-25973: Fix segfault when an invalid nonlocal statement binds a name starting with two underscores.
- bpo-22995: Instances of extension types with a state that aren’t subclasses of list or dict and haven’t implemented any pickle-related methods (__reduce__, __reduce_ex__, __getnewargs__, __getnewargs_ex__, or __getstate__), can no longer be pickled. Including memoryview.
- bpo-20440: Massive replacing unsafe attribute setting code with special macro Py_SETREF.
- bpo-25766: Special method __bytes__() now works in str subclasses.
- bpo-25421: __sizeof__ methods of builtin types now use dynamic basic size. This allows sys.getsize() to work correctly with their subclasses with __slots__ defined.
- bpo-25709: Fixed problem with in-place string concatenation and utf-8 cache.
- bpo-5319: New Py_FinalizeEx() API allowing Python to set an exit status of 120 on failure to flush buffered streams.
- bpo-25485: telnetlib.Telnet is now a context manager.
- bpo-24097: Fixed crash in object.__reduce__() if slot name is freed inside __getattr__.
- bpo-24731: Fixed crash on converting objects with special methods __bytes__, __trunc__, and __float__ returning instances of subclasses of bytes, int, and float to subclasses of bytes, int, and float correspondingly.
- bpo-25630: Fix a possible segfault during argument parsing in functions that accept filesystem paths.
- bpo-23564: Fixed a partially broken sanity check in the _posixsubprocess internals regarding how fds_to_pass were passed to the child. The bug had no actual impact as subprocess.py already avoided it.
- bpo-25388: Fixed tokenizer crash when processing undecodable source code with a null byte.
- bpo-25462: The hash of the key now is calculated only once in most operations in C implementation of OrderedDict.
- bpo-22995: Default implementation of __reduce__ and __reduce_ex__ now rejects builtin types with not defined __new__.
- bpo-24802: Avoid buffer overreads when int(), float(), compile(), exec() and eval() are passed bytes-like objects. These objects are not necessarily terminated by a null byte, but the functions assumed they were.
- bpo-25555: Fix parser and AST: fill lineno and col_offset of “arg” node when compiling AST from Python objects.
- bpo-24726: Fixed a crash and leaking NULL in repr() of OrderedDict that was mutated by direct calls of dict methods.
- bpo-25449: Iterating OrderedDict with keys with unstable hash now raises KeyError in C implementations as well as in Python implementation.
- bpo-25395: Fixed crash when highly nested OrderedDict structures were garbage collected.
- bpo-25401: Optimize bytes.fromhex() and bytearray.fromhex(): they are now between 2x and 3.5x faster.
- bpo-25399: Optimize bytearray % args using the new private _PyBytesWriter API. Formatting is now between 2.5 and 5 times faster.
- bpo-25274: sys.setrecursionlimit() now raises a RecursionError if the new recursion limit is too low depending at the current recursion depth. Modify also the “lower-water mark” formula to make it monotonic. This mark is used to decide when the overflowed flag of the thread state is reset.
- bpo-24402: Fix input() to prompt to the redirected stdout when sys.stdout.fileno() fails.
- bpo-25349: Optimize bytes % args using the new private _PyBytesWriter API. Formatting is now up to 2 times faster.
- bpo-24806: Prevent builtin types that are not allowed to be subclassed from being subclassed through multiple inheritance.
- bpo-25301: The UTF-8 decoder is now up to 15 times as fast for error handlers: `ignore`, `replace` and `surrogateescape`.
- bpo-24848: Fixed a number of bugs in UTF-7 decoding of misformed data.
- bpo-25267: The UTF-8 encoder is now up to 75 times as fast for error handlers: `ignore`, `replace`, `surrogateescape`, `surrogatepass`. Patch co-written with Serhiy Storchaka.
- bpo-25280: Import trace messages emitted in verbose (-v) mode are no longer formatted twice.
- bpo-25227: Optimize ASCII and latin1 encoders with the `surrogateescape` error handler: the encoders are now up to 3 times as fast. Initial patch written by Serhiy Storchaka.
- bpo-25003: On Solaris 11.3 or newer, os.urandom() now uses the getrandom() function instead of the getentropy() function. The getentropy() function is blocking to generate very good quality entropy, os.urandom() doesn’t need such high-quality entropy.
- bpo-9232: Modify Python’s grammar to allow trailing commas in the argument list of a function declaration. For example, “def f(*, a = 3,): pass” is now legal. Patch from Mark Dickinson.
- bpo-24965: Implement PEP 498 “Literal String Interpolation”. This allows you to embed expressions inside f-strings, which are converted to normal strings at run time. Given x=3, then f’value={x}’ == ‘value=3’. Patch by Eric V. Smith.
- bpo-26478: Fix semantic bugs when using binary operators with dictionary views and tuples.
- bpo-26171: Fix possible integer overflow and heap corruption in zipimporter.get_data().
- bpo-25660: Fix TAB key behaviour in REPL with readline.
- bpo-26288: Optimize PyLong_AsDouble.
- bpo-26289: Optimize floor and modulo division for single-digit longs. Microbenchmarks show 2-2.5x improvement. Built-in ‘divmod’ function is now also ~10% faster. (See also: bpo-26315)
- bpo-25887: Raise a RuntimeError when a coroutine object is awaited more than once.

### Library

- bpo-27057: Fix os.set_inheritable() on Android, ioctl() is blocked by SELinux and fails with EACCESS. The function now falls back to fcntl(). Patch written by Michał Bednarski.

- bpo-27014: Fix infinite recursion using typing.py. Thanks to Kalle Tuure!

- bpo-27031: Removed dummy methods in Tkinter widget classes: tk_menuBar() and tk_bindForTraversal().

- bpo-14132: Fix urllib.request redirect handling when the target only has a query string. Original fix by Ján Janech.

- bpo-17214: The “urllib.request” module now percent-encodes non-ASCII bytes found in redirect target URLs. Some servers send Location header fields with non-ASCII bytes, but “http.client” requires the request target to be ASCII-encodable, otherwise a UnicodeEncodeError is raised. Based on patch by Christian Heimes.

- bpo-27033: The default value of the decode_data parameter for smtpd.SMTPChannel and smtpd.SMTPServer constructors is changed to False.

- bpo-27034: Removed deprecated class asynchat.fifo.

- bpo-26870: Added readline.set_auto_history(), which can stop entries being automatically added to the history list. Based on patch by Tyler Crompton.

- bpo-26039: zipfile.ZipFile.open() can now be used to write data into a ZIP file, as well as for extracting data. Patch by Thomas Kluyver.

- bpo-26892: Honor debuglevel flag in urllib.request.HTTPHandler. Patch contributed by Chi Hsuan Yen.

- bpo-22274: In the subprocess module, allow stderr to be redirected to stdout even when stdout is not redirected. Patch by Akira Li.

- bpo-26807: mock_open ‘files’ no longer error on readline at end of file. Patch from Yolanda Robla.

- bpo-25745: Fixed leaking a userptr in curses panel destructor.

- bpo-26977: Removed unnecessary, and ignored, call to sum of squares helper in statistics.pvariance.

- bpo-26002: Use bisect in statistics.median instead of a linear search. Patch by Upendra Kuma.

- bpo-25974: Make use of new Decimal.as_integer_ratio() method in statistics module. Patch by Stefan Krah.

- bpo-26996: Add secrets module as described in PEP 506.

- bpo-26881: The modulefinder module now supports extended opcode arguments.

- bpo-23815: Fixed crashes related to directly created instances of types in _tkinter and curses.panel modules.

- bpo-17765: weakref.ref() no longer silently ignores keyword arguments. Patch by Georg Brandl.

- bpo-26873: xmlrpc now raises ResponseError on unsupported type tags instead of silently return incorrect result.

- bpo-26915: The __contains__ methods in the collections ABCs now check for identity before checking equality. This better matches the behavior of the concrete classes, allows sensible handling of NaNs, and makes it easier to reason about container invariants.

- bpo-26711: Fixed the comparison of plistlib.Data with other types.

- bpo-24114: Fix an uninitialized variable in `ctypes.util`.

  The bug only occurs on SunOS when the ctypes implementation searches for the `crle` program. Patch by Xiang Zhang. Tested on SunOS by Kees Bos.

- bpo-26864: In urllib.request, change the proxy bypass host checking against no_proxy to be case-insensitive, and to not match unrelated host names that happen to have a bypassed hostname as a suffix. Patch by Xiang Zhang.

- bpo-24902: Print server URL on http.server startup. Initial patch by Felix Kaiser.

- bpo-25788: fileinput.hook_encoded() now supports an “errors” argument for passing to open. Original patch by Joseph Hackman.

- bpo-26634: recursive_repr() now sets __qualname__ of wrapper. Patch by Xiang Zhang.

- bpo-26804: urllib.request will prefer lower_case proxy environment variables over UPPER_CASE or Mixed_Case ones. Patch contributed by Hans-Peter Jansen.

- bpo-26837: assertSequenceEqual() now correctly outputs non-stringified differing items (like bytes in the -b mode). This affects assertListEqual() and assertTupleEqual().

- bpo-26041: Remove “will be removed in Python 3.7” from deprecation messages of platform.dist() and platform.linux_distribution(). Patch by Kumaripaba Miyurusara Athukorala.

- bpo-26822: itemgetter, attrgetter and methodcaller objects no longer silently ignore keyword arguments.

- bpo-26733: Disassembling a class now disassembles class and static methods. Patch by Xiang Zhang.

- bpo-26801: Fix error handling in `shutil.get_terminal_size()`, catch `AttributeError` instead of `NameError`. Patch written by Emanuel Barry.

- bpo-24838: tarfile’s ustar and gnu formats now correctly calculate name and link field limits for multibyte character encodings like utf-8.

### Security

- bpo-26657: Fix directory traversal vulnerability with http.server on Windows. This fixes a regression that was introduced in 3.3.4rc1 and 3.4.0rc1. Based on patch by Philipp Hagemeister.

### Library

- bpo-26717: Stop encoding Latin-1-ized WSGI paths with UTF-8. Patch by Anthony Sottile.
- bpo-26782: Add STARTUPINFO to subprocess.__all__ on Windows.
- bpo-26404: Add context manager to socketserver. Patch by Aviv Palivoda.
- bpo-26735: Fix `os.urandom()` on Solaris 11.3 and newer when reading more than 1,024 bytes: call `getrandom()` multiple times with a limit of 1024 bytes per call.
- bpo-26585: Eliminate http.server._quote_html() and use html.escape(quote=False). Patch by Xiang Zhang.
- bpo-26685: Raise OSError if closing a socket fails.
- bpo-16329: Add .webm to mimetypes.types_map. Patch by Giampaolo Rodola’.
- bpo-13952: Add .csv to mimetypes.types_map. Patch by Geoff Wilson.
- bpo-26587: the site module now allows .pth files to specify files to be added to sys.path (e.g. zip files).
- bpo-25609: Introduce contextlib.AbstractContextManager and typing.ContextManager.
- bpo-26709: Fixed Y2038 problem in loading binary PLists.
- bpo-23735: Handle terminal resizing with Readline 6.3+ by installing our own SIGWINCH handler. Patch by Eric Price.
- bpo-25951: Change SSLSocket.sendall() to return None, as explicitly documented for plain socket objects. Patch by Aviv Palivoda.
- bpo-26586: In http.server, respond with “413 Request header fields too large” if there are too many header fields to parse, rather than killing the connection and raising an unhandled exception. Patch by Xiang Zhang.
- bpo-26676: Added missing XMLPullParser to ElementTree.__all__.
- bpo-22854: Change BufferedReader.writable() and BufferedWriter.readable() to always return False.
- bpo-26492: Exhausted iterator of array.array now conforms with the behavior of iterators of other mutable sequences: it lefts exhausted even if iterated array is extended.
- bpo-26641: doctest.DocFileTest and doctest.testfile() now support packages (module splitted into multiple directories) for the package parameter.
- bpo-25195: Fix a regression in mock.MagicMock. _Call is a subclass of tuple (changeset 3603bae63c13 only works for classes) so we need to implement __ne__ ourselves. Patch by Andrew Plummer.
- bpo-26644: Raise ValueError rather than SystemError when a negative length is passed to SSLSocket.recv() or read().
- bpo-23804: Fix SSL recv(0) and read(0) methods to return zero bytes instead of up to 1024.
- bpo-26616: Fixed a bug in datetime.astimezone() method.
- bpo-26637: The `importlib` module now emits an `ImportError` rather than a `TypeError` if `__import__()` is tried during the Python shutdown process but `sys.path` is already cleared (set to `None`).
- bpo-21925: `warnings.formatwarning()` now catches exceptions when calling `linecache.getline()` and `tracemalloc.get_object_traceback()` to be able to log `ResourceWarning` emitted late during the Python shutdown process.
- bpo-23848: On Windows, faulthandler.enable() now also installs an exception handler to dump the traceback of all Python threads on any Windows exception, not only on UNIX signals (SIGSEGV, SIGFPE, SIGABRT).
- bpo-26530: Add C functions `_PyTraceMalloc_Track()` and `_PyTraceMalloc_Untrack()` to track memory blocks using the `tracemalloc` module. Add `_PyTraceMalloc_GetTraceback()` to get the traceback of an object.
- bpo-26588: The _tracemalloc now supports tracing memory allocations of multiple address spaces (domains).
- bpo-24266: Ctrl+C during Readline history search now cancels the search mode when compiled with Readline 7.
- bpo-26590: Implement a safe finalizer for the _socket.socket type. It now releases the GIL to close the socket.
- bpo-18787: spwd.getspnam() now raises a PermissionError if the user doesn’t have privileges.
- bpo-26560: Avoid potential ValueError in BaseHandler.start_response. Initial patch by Peter Inglesby.
- bpo-26567: Add a new function `PyErr_ResourceWarning()` function to pass the destroyed object. Add a source attribute to `warnings.WarningMessage`. Add warnings._showwarnmsg() which uses tracemalloc to get the traceback where source object was allocated.

### Security

- bpo-26313: ssl.py _load_windows_store_certs fails if windows cert store is empty. Patch by Baji.

### Library

- bpo-26569: Fix `pyclbr.readmodule()` and `pyclbr.readmodule_ex()` to support importing packages.
- bpo-26499: Account for remaining Content-Length in HTTPResponse.readline() and read1(). Based on patch by Silent Ghost. Also document that HTTPResponse now supports these methods.
- bpo-25320: Handle sockets in directories unittest discovery is scanning. Patch from Victor van den Elzen.
- bpo-16181: cookiejar.http2time() now returns None if year is higher than datetime.MAXYEAR.
- bpo-26513: Fixes platform module detection of Windows Server
- bpo-23718: Fixed parsing time in week 0 before Jan 1. Original patch by Tamás Bence Gedai.
- bpo-26323: Add Mock.assert_called() and Mock.assert_called_once() methods to unittest.mock. Patch written by Amit Saha.
- bpo-20589: Invoking Path.owner() and Path.group() on Windows now raise NotImplementedError instead of ImportError.
- bpo-26177: Fixed the keys() method for Canvas and Scrollbar widgets.
- bpo-15068: Got rid of excessive buffering in fileinput. The bufsize parameter is now deprecated and ignored.
- bpo-19475: Added an optional argument timespec to the datetime isoformat() method to choose the precision of the time component.
- bpo-2202: Fix UnboundLocalError in AbstractDigestAuthHandler.get_algorithm_impls. Initial patch by Mathieu Dupuy.
- bpo-26167: Minimized overhead in copy.copy() and copy.deepcopy(). Optimized copying and deepcopying bytearrays, NotImplemented, slices, short lists, tuples, dicts, sets.
- bpo-25718: Fixed pickling and copying the accumulate() iterator with total is None.
- bpo-26475: Fixed debugging output for regular expressions with the (?x) flag.
- bpo-26482: Allowed pickling recursive dequeues.
- bpo-26335: Make mmap.write() return the number of bytes written like other write methods. Patch by Jakub Stasiak.
- bpo-26457: Fixed the subnets() methods in IP network classes for the case when resulting prefix length is equal to maximal prefix length. Based on patch by Xiang Zhang.
- bpo-26385: Remove the file if the internal open() call in NamedTemporaryFile() fails. Patch by Silent Ghost.
- bpo-26402: Fix XML-RPC client to retry when the server shuts down a persistent connection. This was a regression related to the new http.client.RemoteDisconnected exception in 3.5.0a4.
- bpo-25913: Leading `<~` is optional now in base64.a85decode() with adobe=True. Patch by Swati Jaiswal.
- bpo-26186: Remove an invalid type check in importlib.util.LazyLoader.
- bpo-26367: importlib.__import__() raises ImportError like builtins.__import__() when `level` is specified but without an accompanying package specified.
- bpo-26309: In the “socketserver” module, shut down the request (closing the connected socket) when verify_request() returns false. Patch by Aviv Palivoda.
- bpo-23430: Change the socketserver module to only catch exceptions raised from a request handler that are derived from Exception (instead of BaseException). Therefore SystemExit and KeyboardInterrupt no longer trigger the handle_error() method, and will now to stop a single-threaded server.

### Security

- bpo-25939: On Windows open the cert store readonly in ssl.enum_certificates.

### Library

- bpo-25995: os.walk() no longer uses FDs proportional to the tree depth.
- bpo-25994: Added the close() method and the support of the context manager protocol for the os.scandir() iterator.
- bpo-23992: multiprocessing: make MapResult not fail-fast upon exception.
- bpo-26243: Support keyword arguments to zlib.compress(). Patch by Aviv Palivoda.
- bpo-26117: The os.scandir() iterator now closes file descriptor not only when the iteration is finished, but when it was failed with error.
- bpo-25949: __dict__ for an OrderedDict instance is now created only when needed.
- bpo-25911: Restored support of bytes paths in os.walk() on Windows.
- bpo-26045: Add UTF-8 suggestion to error message when posting a non-Latin-1 string with http.client.
- bpo-26039: Added zipfile.ZipInfo.from_file() and zipinfo.ZipInfo.is_dir(). Patch by Thomas Kluyver.
- bpo-12923: Reset FancyURLopener’s redirect counter even if there is an exception. Based on patches by Brian Brazil and Daniel Rocco.
- bpo-25945: Fixed a crash when unpickle the functools.partial object with wrong state. Fixed a leak in failed functools.partial constructor. “args” and “keywords” attributes of functools.partial have now always types tuple and dict correspondingly.
- bpo-26202: copy.deepcopy() now correctly copies range() objects with non-atomic attributes.
- bpo-23076: Path.glob() now raises a ValueError if it’s called with an invalid pattern. Patch by Thomas Nyberg.
- bpo-19883: Fixed possible integer overflows in zipimport.
- bpo-26227: On Windows, getnameinfo(), gethostbyaddr() and gethostbyname_ex() functions of the socket module now decode the hostname from the ANSI code page rather than UTF-8.
- bpo-26099: The site module now writes an error into stderr if sitecustomize module can be imported but executing the module raise an ImportError. Same change for usercustomize.
- bpo-26147: xmlrpc now works with strings not encodable with used non-UTF-8 encoding.
- bpo-25935: Garbage collector now breaks reference loops with OrderedDict.
- bpo-16620: Fixed AttributeError in msilib.Directory.glob().
- bpo-26013: Added compatibility with broken protocol 2 pickles created in old Python 3 versions (3.4.3 and lower).
- bpo-26129: Deprecated accepting non-integers in grp.getgrgid().
- bpo-25850: Use cross-compilation by default for 64-bit Windows.
- bpo-25822: Add docstrings to the fields of urllib.parse results. Patch contributed by Swati Jaiswal.
- bpo-22642: Convert trace module option parsing mechanism to argparse. Patch contributed by SilentGhost.
- bpo-24705: Fix sysconfig._parse_makefile not expanding ${} vars appearing before $() vars.
- bpo-26069: Remove the deprecated apis in the trace module.
- bpo-22138: Fix mock.patch behavior when patching descriptors. Restore original values after patching. Patch contributed by Sean McCully.
- bpo-25672: In the ssl module, enable the SSL_MODE_RELEASE_BUFFERS mode option if it is safe to do so.
- bpo-26012: Don’t traverse into symlinks for `**` pattern in pathlib.Path.[r]glob().
- bpo-24120: Ignore PermissionError when traversing a tree with pathlib.Path.[r]glob(). Patch by Ulrich Petri.
- bpo-21815: Accept ] characters in the data portion of imap responses, in order to handle the flags with square brackets accepted and produced by servers such as gmail.
- bpo-25447: fileinput now uses sys.stdin as-is if it does not have a buffer attribute (restores backward compatibility).
- bpo-25971: Optimized creating Fractions from floats by 2 times and from Decimals by 3 times.
- bpo-25802: Document as deprecated the remaining implementations of importlib.abc.Loader.load_module().
- bpo-25928: Add Decimal.as_integer_ratio().
- bpo-25447: Copying the lru_cache() wrapper object now always works, independently from the type of the wrapped object (by returning the original object unchanged).
- bpo-25768: Have the functions in compileall return booleans instead of ints and add proper documentation and tests for the return values.
- bpo-24103: Fixed possible use after free in ElementTree.XMLPullParser.
- bpo-25860: os.fwalk() no longer skips remaining directories when error occurs. Original patch by Samson Lee.
- bpo-25914: Fixed and simplified OrderedDict.__sizeof__.
- bpo-25869: Optimized deepcopying ElementTree; it is now 20 times faster.
- bpo-25873: Optimized iterating ElementTree. Iterating elements Element.iter() is now 40% faster, iterating text Element.itertext() is now up to 2.5 times faster.
- bpo-25902: Fixed various refcount issues in ElementTree iteration.
- bpo-22227: The TarFile iterator is reimplemented using generator. This implementation is simpler that using class.
- bpo-25638: Optimized ElementTree.iterparse(); it is now 2x faster. Optimized ElementTree parsing; it is now 10% faster.
- bpo-25761: Improved detecting errors in broken pickle data.
- bpo-25717: Restore the previous behaviour of tolerating most fstat() errors when opening files. This was a regression in 3.5a1, and stopped anonymous temporary files from working in special cases.
- bpo-24903: Fix regression in number of arguments compileall accepts when ‘-d’ is specified. The check on the number of arguments has been dropped completely as it never worked correctly anyway.
- bpo-25764: In the subprocess module, preserve any exception caused by fork() failure when preexec_fn is used.
- bpo-25771: Tweak the exception message for importlib.util.resolve_name() when ‘package’ isn’t specified but necessary.
- bpo-6478: _strptime’s regexp cache now is reset after changing timezone with time.tzset().
- bpo-14285: When executing a package with the “python -m package” option, and package initialization fails, a proper traceback is now reported. The “runpy” module now lets exceptions from package initialization pass back to the caller, rather than raising ImportError.
- bpo-19771: Also in runpy and the “-m” option, omit the irrelevant message “… is a package and cannot be directly executed” if the package could not even be initialized (e.g. due to a bad `*.pyc` file).
- bpo-25177: Fixed problem with the mean of very small and very large numbers. As a side effect, statistics.mean and statistics.variance should be significantly faster.
- bpo-25718: Fixed copying object with state with boolean value is false.
- bpo-10131: Fixed deep copying of minidom documents. Based on patch by Marian Ganisin.
- bpo-7990: dir() on ElementTree.Element now lists properties: “tag”, “text”, “tail” and “attrib”. Original patch by Santoso Wijaya.
- bpo-25725: Fixed a reference leak in pickle.loads() when unpickling invalid data including tuple instructions.
- bpo-25663: In the Readline completer, avoid listing duplicate global names, and search the global namespace before searching builtins.
- bpo-25688: Fixed file leak in ElementTree.iterparse() raising an error.
- bpo-23914: Fixed SystemError raised by unpickler on broken pickle data.
- bpo-25691: Fixed crash on deleting ElementTree.Element attributes.
- bpo-25624: ZipFile now always writes a ZIP_STORED header for directory entries. Patch by Dingyuan Wang.
- bpo-25626: Change three zlib functions to accept sizes that fit in Py_ssize_t, but internally cap those sizes to UINT_MAX. This resolves a regression in 3.5 where GzipFile.read() failed to read chunks larger than 2 or 4 GiB. The change affects the zlib.Decompress.decompress() max_length parameter, the zlib.decompress() bufsize parameter, and the zlib.Decompress.flush() length parameter.
- bpo-25583: Avoid incorrect errors raised by os.makedirs(exist_ok=True) when the OS gives priority to errors such as EACCES over EEXIST.
- bpo-25593: Change semantics of EventLoop.stop() in asyncio.
- bpo-6973: When we know a subprocess.Popen process has died, do not allow the send_signal(), terminate(), or kill() methods to do anything as they could potentially signal a different process.
- bpo-23883: Added missing APIs to __all__ to match the documented APIs for the following modules: calendar, csv, enum, fileinput, ftplib, logging, optparse, tarfile, threading and wave. Also added a test.support.check__all__() helper. Patches by Jacek Kołodziej, Mauro S. M. Rodrigues and Joel Taddei.
- bpo-25590: In the Readline completer, only call getattr() once per attribute. Also complete names of attributes such as properties and slots which are listed by dir() but not yet created on an instance.
- bpo-25498: Fix a crash when garbage-collecting ctypes objects created by wrapping a memoryview. This was a regression made in 3.5a1. Based on patch by Eryksun.
- bpo-25584: Added “escape” to the __all__ list in the glob module.
- bpo-25584: Fixed recursive glob() with patterns starting with `**`.
- bpo-25446: Fix regression in smtplib’s AUTH LOGIN support.
- bpo-18010: Fix the pydoc web server’s module search function to handle exceptions from importing packages.
- bpo-25554: Got rid of circular references in regular expression parsing.
- bpo-18973: Command-line interface of the calendar module now uses argparse instead of optparse.
- bpo-25510: fileinput.FileInput.readline() now returns b’’ instead of ‘’ at the end if the FileInput was opened with binary mode. Patch by Ryosuke Ito.
- bpo-25503: Fixed inspect.getdoc() for inherited docstrings of properties. Original patch by John Mark Vandenberg.
- bpo-25515: Always use os.urandom as a source of randomness in uuid.uuid4.
- bpo-21827: Fixed textwrap.dedent() for the case when largest common whitespace is a substring of smallest leading whitespace. Based on patch by Robert Li.
- bpo-25447: The lru_cache() wrapper objects now can be copied and pickled (by returning the original object unchanged).
- bpo-25390: typing: Don’t crash on Union[str, Pattern].
- bpo-25441: asyncio: Raise error from drain() when socket is closed.
- bpo-25410: Cleaned up and fixed minor bugs in C implementation of OrderedDict.
- bpo-25411: Improved Unicode support in SMTPHandler through better use of the email package. Thanks to user simon04 for the patch.
- Move the imp module from a PendingDeprecationWarning to DeprecationWarning.
- bpo-25407: Remove mentions of the formatter module being removed in Python 3.6.
- bpo-25406: Fixed a bug in C implementation of OrderedDict.move_to_end() that caused segmentation fault or hang in iterating after moving several items to the start of ordered dict.
- bpo-25382: pickletools.dis() now outputs implicit memo index for the MEMOIZE opcode.
- bpo-25357: Add an optional newline parameter to binascii.b2a_base64(). base64.b64encode() uses it to avoid a memory copy.
- bpo-24164: Objects that need calling `__new__` with keyword arguments, can now be pickled using pickle protocols older than protocol version 4.
- bpo-25364: zipfile now works in threads disabled builds.
- bpo-25328: smtpd’s SMTPChannel now correctly raises a ValueError if both decode_data and enable_SMTPUTF8 are set to true.
- bpo-16099: RobotFileParser now supports Crawl-delay and Request-rate extensions. Patch by Nikolay Bogoychev.
- bpo-25316: distutils raises OSError instead of DistutilsPlatformError when MSVC is not installed.
- bpo-25380: Fixed protocol for the STACK_GLOBAL opcode in pickletools.opcodes.
- bpo-23972: Updates asyncio datagram create method allowing reuseport and reuseaddr socket options to be set prior to binding the socket. Mirroring the existing asyncio create_server method the reuseaddr option for datagram sockets defaults to True if the O/S is ‘posix’ (except if the platform is Cygwin). Patch by Chris Laws.
- bpo-25304: Add asyncio.run_coroutine_threadsafe(). This lets you submit a coroutine to a loop from another thread, returning a concurrent.futures.Future. By Vincent Michel.
- bpo-25232: Fix CGIRequestHandler to split the query from the URL at the first question mark (?) rather than the last. Patch from Xiang Zhang.
- bpo-24657: Prevent CGIRequestHandler from collapsing slashes in the query part of the URL as if it were a path. Patch from Xiang Zhang.
- bpo-25287: Don’t add crypt.METHOD_CRYPT to crypt.methods if it’s not supported. Check if it is supported, it may not be supported on OpenBSD for example.
- bpo-23600: Default implementation of tzinfo.fromutc() was returning wrong results in some cases.
- bpo-25203: Failed readline.set_completer_delims() no longer left the module in inconsistent state.
- bpo-25011: rlcompleter now omits private and special attribute names unless the prefix starts with underscores.
- bpo-25209: rlcompleter now can add a space or a colon after completed keyword.
- bpo-22241: timezone.utc name is now plain ‘UTC’, not ‘UTC-00:00’.
- bpo-23517: fromtimestamp() and utcfromtimestamp() methods of datetime.datetime now round microseconds to nearest with ties going to nearest even integer (ROUND_HALF_EVEN), as round(float), instead of rounding towards -Infinity (ROUND_FLOOR).
- bpo-23552: Timeit now warns when there is substantial (4x) variance between best and worst times. Patch from Serhiy Storchaka.
- bpo-24633: site-packages/README -> README.txt.
- bpo-24879: help() and pydoc can now list named tuple fields in the order they were defined rather than alphabetically. The ordering is determined by the _fields attribute if present.
- bpo-24874: Improve speed of itertools.cycle() and make its pickle more compact.
- Fix crash in itertools.cycle.__setstate__() when the first argument wasn’t a list.
- bpo-20059: urllib.parse raises ValueError on all invalid ports. Patch by Martin Panter.
- bpo-24360: Improve __repr__ of argparse.Namespace() for invalid identifiers. Patch by Matthias Bussonnier.
- bpo-23426: run_setup was broken in distutils. Patch from Alexander Belopolsky.
- bpo-13938: 2to3 converts StringTypes to a tuple. Patch from Mark Hammond.
- bpo-2091: open() accepted a ‘U’ mode string containing ‘+’, but ‘U’ can only be used with ‘r’. Patch from Jeff Balogh and John O’Connor.
- bpo-8585: improved tests for zipimporter2. Patch from Mark Lawrence.
- bpo-18622: unittest.mock.mock_open().reset_mock would recurse infinitely. Patch from Nicola Palumbo and Laurent De Buyst.
- bpo-24426: Fast searching optimization in regular expressions now works for patterns that starts with capturing groups. Fast searching optimization now can’t be disabled at compile time.
- bpo-23661: unittest.mock side_effects can now be exceptions again. This was a regression vs Python 3.4. Patch from Ignacio Rossi
- bpo-13248: Remove deprecated inspect.getmoduleinfo function.
- bpo-25578: Fix (another) memory leak in SSLSocket.getpeercer().
- bpo-25530: Disable the vulnerable SSLv3 protocol by default when creating ssl.SSLContext.
- bpo-25569: Fix memory leak in SSLSocket.getpeercert().
- bpo-25471: Sockets returned from accept() shouldn’t appear to be nonblocking.
- bpo-25319: When threading.Event is reinitialized, the underlying condition should use a regular lock rather than a recursive lock.
- Skip getaddrinfo if host is already resolved. Patch by A. Jesse Jiryu Davis.
- bpo-26050: Add asyncio.StreamReader.readuntil() method. Patch by Марк Коренберг.
- bpo-25924: Avoid unnecessary serialization of getaddrinfo(3) calls on OS X versions 10.5 or higher. Original patch by A. Jesse Jiryu Davis.
- bpo-26406: Avoid unnecessary serialization of getaddrinfo(3) calls on current versions of OpenBSD and NetBSD. Patch by A. Jesse Jiryu Davis.
- bpo-26848: Fix asyncio/subprocess.communicate() to handle empty input. Patch by Jack O’Connor.
- bpo-27040: Add loop.get_exception_handler method
- bpo-27041: asyncio: Add loop.create_future method

### IDLE

- bpo-20640: Add tests for idlelib.configHelpSourceEdit. Patch by Saimadhav Heblikar.
- In the ‘IDLE-console differences’ section of the IDLE doc, clarify how running with IDLE affects sys.modules and the standard streams.
- bpo-25507: fix incorrect change in IOBinding that prevented printing. Augment IOBinding htest to include all major IOBinding functions.
- bpo-25905: Revert unwanted conversion of ‘ to ’ RIGHT SINGLE QUOTATION MARK in README.txt and open this and NEWS.txt with ‘ascii’. Re-encode CREDITS.txt to utf-8 and open it with ‘utf-8’.
- bpo-15348: Stop the debugger engine (normally in a user process) before closing the debugger window (running in the IDLE process). This prevents the RuntimeErrors that were being caught and ignored.
- bpo-24455: Prevent IDLE from hanging when a) closing the shell while the debugger is active (15347); b) closing the debugger with the [X] button (15348); and c) activating the debugger when already active (24455). The patch by Mark Roseman does this by making two changes. 1. Suspend and resume the gui.interaction method with the tcl vwait mechanism intended for this purpose (instead of root.mainloop & .quit). 2. In gui.run, allow any existing interaction to terminate first.
- Change ‘The program’ to ‘Your program’ in an IDLE ‘kill program?’ message to make it clearer that the program referred to is the currently running user program, not IDLE itself.
- bpo-24750: Improve the appearance of the IDLE editor window status bar. Patch by Mark Roseman.
- bpo-25313: Change the handling of new built-in text color themes to better address the compatibility problem introduced by the addition of IDLE Dark. Consistently use the revised idleConf.CurrentTheme everywhere in idlelib.
- bpo-24782: Extension configuration is now a tab in the IDLE Preferences dialog rather than a separate dialog. The former tabs are now a sorted list. Patch by Mark Roseman.
- bpo-22726: Re-activate the config dialog help button with some content about the other buttons and the new IDLE Dark theme.
- bpo-24820: IDLE now has an ‘IDLE Dark’ built-in text color theme. It is more or less IDLE Classic inverted, with a cobalt blue background. Strings, comments, keywords, … are still green, red, orange, … . To use it with IDLEs released before November 2015, hit the ‘Save as New Custom Theme’ button and enter a new name, such as ‘Custom Dark’. The custom theme will work with any IDLE release, and can be modified.
- bpo-25224: README.txt is now an idlelib index for IDLE developers and curious users. The previous user content is now in the IDLE doc chapter. ‘IDLE’ now means ‘Integrated Development and Learning Environment’.
- bpo-24820: Users can now set breakpoint colors in Settings -> Custom Highlighting. Original patch by Mark Roseman.
- bpo-24972: Inactive selection background now matches active selection background, as configured by users, on all systems. Found items are now always highlighted on Windows. Initial patch by Mark Roseman.
- bpo-24570: Idle: make calltip and completion boxes appear on Macs affected by a tk regression. Initial patch by Mark Roseman.
- bpo-24988: Idle ScrolledList context menus (used in debugger) now work on Mac Aqua. Patch by Mark Roseman.
- bpo-24801: Make right-click for context menu work on Mac Aqua. Patch by Mark Roseman.
- bpo-25173: Associate tkinter messageboxes with a specific widget. For Mac OSX, make them a ‘sheet’. Patch by Mark Roseman.
- bpo-25198: Enhance the initial html viewer now used for Idle Help. Properly indent fixed-pitch text (patch by Mark Roseman). Give code snippet a very Sphinx-like light blueish-gray background. Re-use initial width and height set by users for shell and editor. When the Table of Contents (TOC) menu is used, put the section header at the top of the screen.
- bpo-25225: Condense and rewrite Idle doc section on text colors.
- bpo-21995: Explain some differences between IDLE and console Python.
- bpo-22820: Explain need for print when running file from Idle editor.
- bpo-25224: Doc: augment Idle feature list and no-subprocess section.
- bpo-25219: Update doc for Idle command line options. Some were missing and notes were not correct.
- bpo-24861: Most of idlelib is private and subject to change. Use idleib.idle.* to start Idle. See idlelib.__init__.__doc__.
- bpo-25199: Idle: add synchronization comments for future maintainers.
- bpo-16893: Replace help.txt with help.html for Idle doc display. The new idlelib/help.html is rstripped Doc/build/html/library/idle.html. It looks better than help.txt and will better document Idle as released. The tkinter html viewer that works for this file was written by Rose Roseman. The now unused EditorWindow.HelpDialog class and helt.txt file are deprecated.
- bpo-24199: Deprecate unused idlelib.idlever with possible removal in 3.6.
- bpo-24790: Remove extraneous code (which also create 2 & 3 conflicts).

### Documentation

- bpo-26736: Used HTTPS for external links in the documentation if possible.
- bpo-6953: Rework the Readline module documentation to group related functions together, and add more details such as what underlying Readline functions and variables are accessed.
- bpo-23606: Adds note to ctypes documentation regarding cdll.msvcrt.
- bpo-24952: Clarify the default size argument of stack_size() in the “threading” and “_thread” modules. Patch from Mattip.
- bpo-26014: Update 3.x packaging documentation: * “See also” links to the new docs are now provided in the legacy pages * links to setuptools documentation have been updated

### Tests

- bpo-21916: Added tests for the turtle module. Patch by ingrid, Gregory Loyse and Jelle Zijlstra.
- bpo-26295: When using “python3 -m test –testdir=TESTDIR”, regrtest doesn’t add “test.” prefix to test module names.
- bpo-26523: The multiprocessing thread pool (multiprocessing.dummy.Pool) was untested.
- bpo-26015: Added new tests for pickling iterators of mutable sequences.
- bpo-26325: Added test.support.check_no_resource_warning() to check that no ResourceWarning is emitted.
- bpo-25940: Changed test_ssl to use its internal local server more. This avoids relying on svn.python.org, which recently changed root certificate.
- bpo-25616: Tests for OrderedDict are extracted from test_collections into separate file test_ordered_dict.
- bpo-25449: Added tests for OrderedDict subclasses.
- bpo-25188: Add -P/–pgo to test.regrtest to suppress error output when running the test suite for the purposes of a PGO build. Initial patch by Alecsandru Patrascu.
- bpo-22806: Add `python -m test --list-tests` command to list tests.
- bpo-18174: `python -m test --huntrleaks ...` now also checks for leak of file descriptors. Patch written by Richard Oudkerk.
- bpo-25260: Fix `python -m test --coverage` on Windows. Remove the list of ignored directories.
- `PCbuild\rt.bat` now accepts an unlimited number of arguments to pass along to regrtest.py. Previously there was a limit of 9.
- bpo-26583: Skip test_timestamp_overflow in test_import if bytecode files cannot be written.

### Build

- bpo-21277: Don’t try to link _ctypes with a ffi_convenience library.
- bpo-26884: Fix linking extension modules for cross builds. Patch by Xavier de Gaye.
- bpo-26932: Fixed support of RTLD_* constants defined as enum values, not via macros (in particular on Android). Patch by Chi Hsuan Yen.
- bpo-22359: Disable the rules for running _freeze_importlib and pgen when cross-compiling. The output of these programs is normally saved with the source code anyway, and is still regenerated when doing a native build. Patch by Xavier de Gaye.
- bpo-21668: Link audioop, _datetime, _ctypes_test modules to libm, except on Mac OS X. Patch written by Chi Hsuan Yen.
- bpo-25702: A –with-lto configure option has been added that will enable link time optimizations at build time during a make profile-opt. Some compilers and toolchains are known to not produce stable code when using LTO, be sure to test things thoroughly before relying on it. It can provide a few % speed up over profile-opt alone.
- bpo-26624: Adds validation of ucrtbase[d].dll version with warning for old versions.
- bpo-17603: Avoid error about nonexistant fileblocks.o file by using a lower-level check for st_blocks in struct stat.
- bpo-26079: Fixing the build output folder for tix-8.4.3.6. Patch by Bjoern Thiel.
- bpo-26465: Update Windows builds to use OpenSSL 1.0.2g.
- bpo-25348: Added `--pgo` and `--pgo-job` arguments to `PCbuild\build.bat` for building with Profile-Guided Optimization. The old `PCbuild\build_pgo.bat` script is removed.
- bpo-25827: Add support for building with ICC to `configure`, including a new `--with-icc` flag.
- bpo-25696: Fix installation of Python on UNIX with make -j9.
- bpo-24986: It is now possible to build Python on Windows without errors when external libraries are not available.
- bpo-24421: Compile Modules/_math.c once, before building extensions. Previously it could fail to compile properly if the math and cmath builds were concurrent.
- bpo-26465: Update OS X 10.5+ 32-bit-only installer to build and link with OpenSSL 1.0.2g.
- bpo-26268: Update Windows builds to use OpenSSL 1.0.2f.
- bpo-25136: Support Apple Xcode 7’s new textual SDK stub libraries.
- bpo-24324: Do not enable unreachable code warnings when using gcc as the option does not work correctly in older versions of gcc and has been silently removed as of gcc-4.5.

### Windows

- bpo-27053: Updates make_zip.py to correctly generate library ZIP file.
- bpo-26268: Update the prepare_ssl.py script to handle OpenSSL releases that don’t include the contents of the include directory (that is, 1.0.2e and later).
- bpo-26071: bdist_wininst created binaries fail to start and find 32bit Python
- bpo-26073: Update the list of magic numbers in launcher
- bpo-26065: Excludes venv from library when generating embeddable distro.
- bpo-25022: Removed very outdated PC/example_nt/ directory.

### Tools/Demos

- bpo-26799: Fix python-gdb.py: don’t get C types once when the Python code is loaded, but get C types on demand. The C types can change if python-gdb.py is loaded before the Python executable. Patch written by Thomas Ilsche.
- bpo-26271: Fix the Freeze tool to properly use flags passed through configure. Patch by Daniel Shaulov.
- bpo-26489: Add dictionary unpacking support to Tools/parser/unparse.py. Patch by Guo Ci Teo.
- bpo-26316: Fix variable name typo in Argument Clinic.
- bpo-25440: Fix output of python-config –extension-suffix.
- bpo-25154: The pyvenv script has been deprecated in favour of `python3 -m venv`.

### C API

- bpo-26312: SystemError is now raised in all programming bugs with using PyArg_ParseTupleAndKeywords(). RuntimeError did raised before in some programming bugs.
- bpo-26198: ValueError is now raised instead of TypeError on buffer overflow in parsing “es#” and “et#” format units. SystemError is now raised instead of TypeError on programmatical error in parsing format string.

## Python 3.5.5 final

Release date: 2018-02-04

There were no new changes in version 3.5.5.

## Python 3.5.5 release candidate 1

Release date: 2018-01-23

### Security

- bpo-32551: The `sys.path[0]` initialization change for bpo-29139 caused a regression by revealing an inconsistency in how sys.path is initialized when executing `__main__` from a zipfile, directory, or other import location. This is considered a potential security issue, as it may lead to privileged processes unexpectedly loading code from user controlled directories in situations where that was not previously the case.

  The interpreter now consistently avoids ever adding the import location’s parent directory to `sys.path`, and ensures no other `sys.path` entries are inadvertently modified when inserting the import location named on the command line. (Originally reported as bpo-29723 against Python 3.6rc1, but it was missed at the time that the then upcoming Python 3.5.4 release would also be affected)

- bpo-30657: Fixed possible integer overflow in PyBytes_DecodeEscape, CVE-2017-1000158. Original patch by Jay Bosamiya; rebased to Python 3 by Miro Hrončok.

- bpo-30947: Upgrade libexpat embedded copy from version 2.2.1 to 2.2.3 to get security fixes.

### Core and Builtins

- bpo-31095: Fix potential crash during GC caused by `tp_dealloc` which doesn’t call `PyObject_GC_UnTrack()`.

### Library

- bpo-32072: Fixed issues with binary plists:
  - Fixed saving bytearrays.
  - Identical objects will be saved only once.
  - Equal references will be load as identical objects.
  - Added support for saving and loading recursive data structures.
- bpo-31170: expat: Update libexpat from 2.2.3 to 2.2.4. Fix copying of partial characters for UTF-8 input (libexpat bug 115): https://github.com/libexpat/libexpat/issues/115

## Python 3.5.4 final

Release date: 2017-08-07

### Library

- bpo-30119: ftplib.FTP.putline() now throws ValueError on commands that contains CR or LF. Patch by Dong-hee Na.

## Python 3.5.4 release candidate 1

Release date: 2017-07-23

### Security

- bpo-30730: Prevent environment variables injection in subprocess on Windows. Prevent passing other environment variables and command arguments.
- bpo-30694: Upgrade expat copy from 2.2.0 to 2.2.1 to get fixes of multiple security vulnerabilities including: CVE-2017-9233 (External entity infinite loop DoS), CVE-2016-9063 (Integer overflow, re-fix), CVE-2016-0718 (Fix regression bugs from 2.2.0’s fix to CVE-2016-0718) and CVE-2012-0876 (Counter hash flooding with SipHash). Note: the CVE-2016-5300 (Use os-specific entropy sources like getrandom) doesn’t impact Python, since Python already gets entropy from the OS to set the expat secret using `XML_SetHashSalt()`.
- bpo-30500: Fix urllib.parse.splithost() to correctly parse fragments. For example, `splithost('//127.0.0.1#@evil.com/')` now correctly returns the `127.0.0.1` host, instead of treating `@evil.com` as the host in an authentication (`login@host`).
- bpo-29591: Update expat copy from 2.1.1 to 2.2.0 to get fixes of CVE-2016-0718 and CVE-2016-4472. See https://sourceforge.net/p/expat/bugs/537/ for more information.

### Core and Builtins

- bpo-30876: Relative import from unloaded package now reimports the package instead of failing with SystemError. Relative import from non-package now fails with ImportError rather than SystemError.
- bpo-30765: Avoid blocking in pthread_mutex_lock() when PyThread_acquire_lock() is asked not to block.
- bpo-27945: Fixed various segfaults with dict when input collections are mutated during searching, inserting or comparing. Based on patches by Duane Griffin and Tim Mitchell.
- bpo-25794: Fixed type.__setattr__() and type.__delattr__() for non-interned attribute names. Based on patch by Eryk Sun.
- bpo-29935: Fixed error messages in the index() method of tuple, list and deque when pass indices of wrong type.
- bpo-28876: `bool(range)` works even if `len(range)` raises `OverflowError`.
- bpo-29600: Fix wrapping coroutine return values in StopIteration.
- bpo-29537: Restore runtime compatibility with bytecode files generated by CPython 3.5.0 to 3.5.2, and adjust the eval loop to avoid the problems that could be caused by the malformed variant of the BUILD_MAP_UNPACK_WITH_CALL opcode that they may contain. Patch by Petr Viktorin, Serhiy Storchaka, and Nick Coghlan.
- bpo-28598: Support __rmod__ for subclasses of str being called before str.__mod__. Patch by Martijn Pieters.
- bpo-29602: Fix incorrect handling of signed zeros in complex constructor for complex subclasses and for inputs having a __complex__ method. Patch by Serhiy Storchaka.
- bpo-29347: Fixed possibly dereferencing undefined pointers when creating weakref objects.
- bpo-29438: Fixed use-after-free problem in key sharing dict.
- bpo-29319: Prevent RunMainFromImporter overwriting sys.path[0].
- bpo-29337: Fixed possible BytesWarning when compare the code objects. Warnings could be emitted at compile time.
- bpo-29478: If max_line_length=None is specified while using the Compat32 policy, it is no longer ignored. Patch by Mircea Cosbuc.

### Library

- bpo-29403: Fix `unittest.mock`’s autospec to not fail on method-bound builtin functions. Patch by Aaron Gallagher.

- bpo-30961: Fix decrementing a borrowed reference in tracemalloc.

- bpo-30886: Fix multiprocessing.Queue.join_thread(): it now waits until the thread completes, even if the thread was started by the same process which created the queue.

- bpo-29854: Fix segfault in readline when using readline’s history-size option. Patch by Nir Soffer.

- bpo-30807: signal.setitimer() may disable the timer when passed a tiny value.

  Tiny values (such as 1e-6) are valid non-zero values for setitimer(), which is specified as taking microsecond-resolution intervals. However, on some platform, our conversion routine could convert 1e-6 into a zero interval, therefore disabling the timer instead of (re-)scheduling it.

- bpo-30441: Fix bug when modifying os.environ while iterating over it

- bpo-30532: Fix email header value parser dropping folding white space in certain cases.

- bpo-29169: Update zlib to 1.2.11.

- bpo-30879: os.listdir() and os.scandir() now emit bytes names when called with bytes-like argument.

- bpo-30746: Prohibited the ‘=’ character in environment variable names in `os.putenv()` and `os.spawn*()`.

- bpo-29755: Fixed the lgettext() family of functions in the gettext module. They now always return bytes.

- bpo-30645: Fix path calculation in imp.load_package(), fixing it for cases when a package is only shipped with bytecodes. Patch by Alexandru Ardelean.

- bpo-23890: unittest.TestCase.assertRaises() now manually breaks a reference cycle to not keep objects alive longer than expected.

- bpo-30149: inspect.signature() now supports callables with variable-argument parameters wrapped with partialmethod. Patch by Dong-hee Na.

- bpo-29931: Fixed comparison check for ipaddress.ip_interface objects. Patch by Sanjay Sundaresan.

- bpo-24484: Avoid race condition in multiprocessing cleanup.

- bpo-28994: The traceback no longer displayed for SystemExit raised in a callback registered by atexit.

- bpo-30508: Don’t log exceptions if Task/Future “cancel()” method was called.

- bpo-28556: Updates to typing module: Add generic AsyncContextManager, add support for ContextManager on all versions. Original PRs by Jelle Zijlstra and Ivan Levkivskyi

- bpo-29870: Fix ssl sockets leaks when connection is aborted in asyncio/ssl implementation. Patch by Michaël Sghaïer.

- bpo-29743: Closing transport during handshake process leaks open socket. Patch by Nikolay Kim

- bpo-27585: Fix waiter cancellation in asyncio.Lock. Patch by Mathieu Sornay.

- bpo-30418: On Windows, subprocess.Popen.communicate() now also ignore EINVAL on stdin.write() if the child process is still running but closed the pipe.

- bpo-30378: Fix the problem that logging.handlers.SysLogHandler cannot handle IPv6 addresses.

- bpo-29960: Preserve generator state when _random.Random.setstate() raises an exception. Patch by Bryan Olson.

- bpo-30414: multiprocessing.Queue._feed background running thread do not break from main loop on exception.

- bpo-30003: Fix handling escape characters in HZ codec. Based on patch by Ma Lin.

- bpo-30301: Fix AttributeError when using SimpleQueue.empty() under spawn and forkserver start methods.

- bpo-30329: imaplib and poplib now catch the Windows socket WSAEINVAL error (code 10022) on shutdown(SHUT_RDWR): An invalid operation was attempted. This error occurs sometimes on SSL connections.

- bpo-30375: Warnings emitted when compile a regular expression now always point to the line in the user code. Previously they could point into inners of the re module if emitted from inside of groups or conditionals.

- bpo-30048: Fixed `Task.cancel()` can be ignored when the task is running coroutine and the coroutine returned without any more `await`.

- bpo-29990: Fix range checking in GB18030 decoder. Original patch by Ma Lin.

- bpo-26293: Change resulted because of zipfile breakage. (See also: bpo-29094)

- bpo-30243: Removed the __init__ methods of _json’s scanner and encoder. Misusing them could cause memory leaks or crashes. Now scanner and encoder objects are completely initialized in the __new__ methods.

- bpo-30185: Avoid KeyboardInterrupt tracebacks in forkserver helper process when Ctrl-C is received.

- bpo-28556: Various updates to typing module: add typing.NoReturn type, use WrapperDescriptorType, minor bug-fixes. Original PRs by Jim Fasarakis-Hilliard and Ivan Levkivskyi.

- bpo-30205: Fix getsockname() for unbound AF_UNIX sockets on Linux.

- bpo-30070: Fixed leaks and crashes in errors handling in the parser module.

- bpo-30061: Fixed crashes in IOBase methods __next__() and readlines() when readline() or __next__() respectively return non-sizeable object. Fixed possible other errors caused by not checking results of PyObject_Size(), PySequence_Size(), or PyMapping_Size().

- bpo-30068: _io._IOBase.readlines will check if it’s closed first when hint is present.

- bpo-29694: Fixed race condition in pathlib mkdir with flags parents=True. Patch by Armin Rigo.

- bpo-29692: Fixed arbitrary unchaining of RuntimeError exceptions in contextlib.contextmanager. Patch by Siddharth Velankar.

- bpo-29998: Pickling and copying ImportError now preserves name and path attributes.

- bpo-29942: Fix a crash in itertools.chain.from_iterable when encountering long runs of empty iterables.

- bpo-27863: Fixed multiple crashes in ElementTree caused by race conditions and wrong types.

- bpo-28699: Fixed a bug in pools in multiprocessing.pool that raising an exception at the very first of an iterable may swallow the exception or make the program hang. Patch by Davin Potts and Xiang Zhang.

- bpo-25803: Avoid incorrect errors raised by Path.mkdir(exist_ok=True) when the OS gives priority to errors such as EACCES over EEXIST.

- bpo-29861: Release references to tasks, their arguments and their results as soon as they are finished in multiprocessing.Pool.

- bpo-29884: faulthandler: Restore the old sigaltstack during teardown. Patch by Christophe Zeitouny.

- bpo-25455: Fixed crashes in repr of recursive buffered file-like objects.

- bpo-29800: Fix crashes in partial.__repr__ if the keys of partial.keywords are not strings. Patch by Michael Seifert.

- bpo-29742: get_extra_info() raises exception if get called on closed ssl transport. Patch by Nikolay Kim.

- bpo-8256: Fixed possible failing or crashing input() if attributes “encoding” or “errors” of sys.stdin or sys.stdout are not set or are not strings.

- bpo-28298: Fix a bug that prevented array ‘Q’, ‘L’ and ‘I’ from accepting big intables (objects that have __int__) as elements. Patch by Oren Milman.

- bpo-29615: SimpleXMLRPCDispatcher no longer chains KeyError (or any other exception) to exception(s) raised in the dispatched methods. Patch by Petr Motejlek.

- bpo-29704: asyncio.subprocess.SubprocessStreamProtocol no longer closes before all pipes are closed.

- bpo-29703: Fix asyncio to support instantiation of new event loops in child processes.

- bpo-29376: Fix assertion error in threading._DummyThread.is_alive().

- bpo-29110: Fix file object leak in aifc.open() when file is given as a filesystem path and is not in valid AIFF format. Patch by Anthony Zhang.

- bpo-28961: Fix unittest.mock._Call helper: don’t ignore the name parameter anymore. Patch written by Jiajun Huang.

- bpo-29532: Altering a kwarg dictionary passed to functools.partial() no longer affects a partial object after creation.

- bpo-28556: Various updates to typing module: typing.Counter, typing.ChainMap, improved ABC caching, etc. Original PRs by Jelle Zijlstra, Ivan Levkivskyi, Manuel Krebber, and Łukasz Langa.

- bpo-29100: Fix datetime.fromtimestamp() regression introduced in Python 3.6.0: check minimum and maximum years.

- bpo-29519: Fix weakref spewing exceptions during interpreter shutdown when used with a rare combination of multiprocessing and custom codecs.

- bpo-29416: Prevent infinite loop in pathlib.Path.mkdir

- bpo-29444: Fixed out-of-bounds buffer access in the group() method of the match object. Based on patch by WGH.

- bpo-29335: Fix subprocess.Popen.wait() when the child process has exited to a stopped instead of terminated state (ex: when under ptrace).

- bpo-29290: Fix a regression in argparse that help messages would wrap at non-breaking spaces.

- bpo-28735: Fixed the comparison of mock.MagickMock with mock.ANY.

- bpo-29011: Fix an important omission by adding Deque to the typing module.

- bpo-29219: Fixed infinite recursion in the repr of uninitialized ctypes.CDLL instances.

- bpo-28969: Fixed race condition in C implementation of functools.lru_cache. KeyError could be raised when cached function with full cache was simultaneously called from differen threads with the same uncached arguments.

- bpo-29142: In urllib.request, suffixes in no_proxy environment variable with leading dots could match related hostnames again (e.g. .b.c matches a.b.c). Patch by Milan Oberkirch.

### Documentation

- bpo-30176: Add missing attribute related constants in curses documentation.
- bpo-26985: Add missing info of code object in inspect documentation.
- bpo-28929: Link the documentation to its source file on GitHub.
- bpo-25008: Document smtpd.py as effectively deprecated and add a pointer to aiosmtpd, a third-party asyncio-based replacement.
- bpo-26355: Add canonical header link on each page to corresponding major version of the documentation. Patch by Matthias Bussonnier.
- bpo-29349: Fix Python 2 syntax in code for building the documentation.

### Tests

- bpo-30822: Fix regrtest command line parser to allow passing -u extralargefile to run test_zipfile64.

- bpo-30383: regrtest: Enhance regrtest and backport features from the master branch.

  Add options: –coverage, –testdir, –list-tests (list test files, don’t run them), –list-cases (list test identifiers, don’t run them, bpo-30523), –matchfile (load a list of test filters from a text file, bpo-30540), –slowest (alias to –slow).

  Enhance output: add timestamp, test result, currently running tests, “Tests result: xxx” summary with total duration, etc.

  Fix reference leak hunting in regrtest, –huntrleaks: regrtest now warms up caches, create explicitly all internal singletons which are created on demand to prevent false positives when checking for reference leaks. (bpo-30675).

- bpo-30357: test_thread: setUp() now uses support.threading_setup() and support.threading_cleanup() to wait until threads complete to avoid random side effects on following tests. Initial patch written by Grzegorz Grzywacz.

- bpo-28087: Skip test_asyncore and test_eintr poll failures on macOS. Skip some tests of select.poll when running on macOS due to unresolved issues with the underlying system poll function on some macOS versions.

- bpo-30197: Enhanced functions swap_attr() and swap_item() in the test.support module. They now work when delete replaced attribute or item inside the with statement. The old value of the attribute or item (or None if it doesn’t exist) now will be assigned to the target of the “as” clause, if there is one.

- bpo-29571: to match the behaviour of the `re.LOCALE` flag, test_re.test_locale_flag now uses `locale.getpreferredencoding(False)` to determine the candidate encoding for the test regex (allowing it to correctly skip the test when the default locale encoding is a multi-byte encoding)

### Build

- bpo-29243: Prevent unnecessary rebuilding of Python during `make test`, `make install` and some other make targets when configured with `--enable-optimizations`.
- bpo-23404: Don’t regenerate generated files based on file modification time anymore: the action is now explicit. Replace `make touch` with `make regen-all`.
- bpo-29643: Fix `--enable-optimization` didn’t work.

### Windows

- bpo-30687: Locate msbuild.exe on Windows when building rather than vcvarsall.bat
- bpo-29392: Prevent crash when passing invalid arguments into msvcrt module.

### C API

- bpo-27867: Function PySlice_GetIndicesEx() is replaced with a macro if Py_LIMITED_API is set to the value between 0x03050400 and 0x03060000 (not including) or 0x03060100 or higher.
- bpo-29083: Fixed the declaration of some public API functions. PyArg_VaParse() and PyArg_VaParseTupleAndKeywords() were not available in limited API. PyArg_ValidateKeywordArguments(), PyArg_UnpackTuple() and Py_BuildValue() were not available in limited API of version < 3.3 when PY_SSIZE_T_CLEAN is defined.

## Python 3.5.3 final

Release date: 2017-01-17

There were no code changes between 3.5.3rc1 and 3.5.3 final.

## Python 3.5.3 release candidate 1

Release date: 2017-01-02

### Core and Builtins

- bpo-29073: bytearray formatting no longer truncates on first null byte.
- bpo-28932: Do not include <sys/random.h> if it does not exist.
- bpo-28147: Fix a memory leak in split-table dictionaries: setattr() must not convert combined table into split table.
- bpo-25677: Correct the positioning of the syntax error caret for indented blocks. Based on patch by Michael Layzell.
- bpo-29000: Fixed bytes formatting of octals with zero padding in alternate form.
- bpo-28512: Fixed setting the offset attribute of SyntaxError by PyErr_SyntaxLocationEx() and PyErr_SyntaxLocationObject().
- bpo-28991: functools.lru_cache() was susceptible to an obscure reentrancy bug caused by a monkey-patched len() function.
- bpo-28648: Fixed crash in Py_DecodeLocale() in debug build on Mac OS X when decode astral characters. Patch by Xiang Zhang.
- bpo-19398: Extra slash no longer added to sys.path components in case of empty compile-time PYTHONPATH components.
- bpo-28426: Fixed potential crash in PyUnicode_AsDecodedObject() in debug build.
- bpo-23782: Fixed possible memory leak in _PyTraceback_Add() and exception loss in PyTraceBack_Here().
- bpo-28379: Added sanity checks and tests for PyUnicode_CopyCharacters(). Patch by Xiang Zhang.
- bpo-28376: The type of long range iterator is now registered as Iterator. Patch by Oren Milman.
- bpo-28376: The constructor of range_iterator now checks that step is not 0. Patch by Oren Milman.
- bpo-26906: Resolving special methods of uninitialized type now causes implicit initialization of the type instead of a fail.
- bpo-18287: PyType_Ready() now checks that tp_name is not NULL. Original patch by Niklas Koep.
- bpo-24098: Fixed possible crash when AST is changed in process of compiling it.
- bpo-28350: String constants with null character no longer interned.
- bpo-26617: Fix crash when GC runs during weakref callbacks.
- bpo-27942: String constants now interned recursively in tuples and frozensets.
- bpo-21578: Fixed misleading error message when ImportError called with invalid keyword args.
- bpo-28203: Fix incorrect type in error message from `complex(1.0, {2:3})`. Patch by Soumya Sharma.
- bpo-27955: Fallback on reading /dev/urandom device when the getrandom() syscall fails with EPERM, for example when blocked by SECCOMP.
- bpo-28131: Fix a regression in zipimport’s compile_source(). zipimport should use the same optimization level as the interpreter.
- bpo-25221: Fix corrupted result from PyLong_FromLong(0) when Python is compiled with NSMALLPOSINTS = 0.
- bpo-25758: Prevents zipimport from unnecessarily encoding a filename (patch by Eryk Sun)
- bpo-28189: dictitems_contains no longer swallows compare errors. (Patch by Xiang Zhang)
- bpo-27812: Properly clear out a generator’s frame’s backreference to the generator to prevent crashes in frame.clear().
- bpo-27811: Fix a crash when a coroutine that has not been awaited is finalized with warnings-as-errors enabled.
- bpo-27587: Fix another issue found by PVS-Studio: Null pointer check after use of ‘def’ in _PyState_AddModule(). Initial patch by Christian Heimes.
- bpo-26020: set literal evaluation order did not match documented behaviour.
- bpo-27782: Multi-phase extension module import now correctly allows the `m_methods` field to be used to add module level functions to instances of non-module types returned from `Py_create_mod`. Patch by Xiang Zhang.
- bpo-27936: The round() function accepted a second None argument for some types but not for others. Fixed the inconsistency by accepting None for all numeric types.
- bpo-27487: Warn if a submodule argument to “python -m” or runpy.run_module() is found in sys.modules after parent packages are imported, but before the submodule is executed.
- bpo-27558: Fix a SystemError in the implementation of “raise” statement. In a brand new thread, raise a RuntimeError since there is no active exception to reraise. Patch written by Xiang Zhang.
- bpo-27419: Standard __import__() no longer look up “__import__” in globals or builtins for importing submodules or “from import”. Fixed handling an error of non-string package name.
- bpo-27083: Respect the PYTHONCASEOK environment variable under Windows.
- bpo-27514: Make having too many statically nested blocks a SyntaxError instead of SystemError.
- bpo-27473: Fixed possible integer overflow in bytes and bytearray concatenations. Patch by Xiang Zhang.
- bpo-27507: Add integer overflow check in bytearray.extend(). Patch by Xiang Zhang.
- bpo-27581: Don’t rely on wrapping for overflow check in PySequence_Tuple(). Patch by Xiang Zhang.
- bpo-27443: __length_hint__() of bytearray iterators no longer return a negative integer for a resized bytearray.
- bpo-27942: Fix memory leak in codeobject.c

### Library

- bpo-15812: inspect.getframeinfo() now correctly shows the first line of a context. Patch by Sam Breese.

- bpo-29094: Offsets in a ZIP file created with extern file object and modes “w” and “x” now are relative to the start of the file.

- bpo-13051: Fixed recursion errors in large or resized curses.textpad.Textbox. Based on patch by Tycho Andersen.

- bpo-29119: Fix weakrefs in the pure python version of collections.OrderedDict move_to_end() method. Contributed by Andra Bogildea.

- bpo-9770: curses.ascii predicates now work correctly with negative integers.

- bpo-28427: old keys should not remove new values from WeakValueDictionary when collecting from another thread.

- bpo-28923: Remove editor artifacts from Tix.py.

- bpo-28871: Fixed a crash when deallocate deep ElementTree.

- bpo-19542: Fix bugs in WeakValueDictionary.setdefault() and WeakValueDictionary.pop() when a GC collection happens in another thread.

- bpo-20191: Fixed a crash in resource.prlimit() when pass a sequence that doesn’t own its elements as limits.

- bpo-28779: multiprocessing.set_forkserver_preload() would crash the forkserver process if a preloaded module instantiated some multiprocessing objects such as locks.

- bpo-28847: dbm.dumb now supports reading read-only files and no longer writes the index file when it is not changed.

- bpo-25659: In ctypes, prevent a crash calling the from_buffer() and from_buffer_copy() methods on abstract classes like Array.

- bpo-28732: Fix crash in os.spawnv() with no elements in args

- bpo-28485: Always raise ValueError for negative compileall.compile_dir(workers=…) parameter, even when multithreading is unavailable.

- bpo-28387: Fixed possible crash in _io.TextIOWrapper deallocator when the garbage collector is invoked in other thread. Based on patch by Sebastian Cufre.

- bpo-27517: LZMA compressor and decompressor no longer raise exceptions if given empty data twice. Patch by Benjamin Fogle.

- bpo-28549: Fixed segfault in curses’s addch() with ncurses6.

- bpo-28449: tarfile.open() with mode “r” or “r:” now tries to open a tar file with compression before trying to open it without compression. Otherwise it had 50% chance failed with ignore_zeros=True.

- bpo-23262: The webbrowser module now supports Firefox 36+ and derived browsers. Based on patch by Oleg Broytman.

- bpo-27939: Fixed bugs in tkinter.ttk.LabeledScale and tkinter.Scale caused by representing the scale as float value internally in Tk. tkinter.IntVar now works if float value is set to underlying Tk variable.

- bpo-28255: calendar.TextCalendar().prmonth() no longer prints a space at the start of new line after printing a month’s calendar. Patch by Xiang Zhang.

- bpo-20491: The textwrap.TextWrapper class now honors non-breaking spaces. Based on patch by Kaarle Ritvanen.

- bpo-28353: os.fwalk() no longer fails on broken links.

- bpo-25464: Fixed HList.header_exists() in tkinter.tix module by addin a workaround to Tix library bug.

- bpo-28488: shutil.make_archive() no longer add entry “./” to ZIP archive.

- bpo-24452: Make webbrowser support Chrome on Mac OS X.

- bpo-20766: Fix references leaked by pdb in the handling of SIGINT handlers.

- bpo-26293: Fixed writing ZIP files that starts not from the start of the file. Offsets in ZIP file now are relative to the start of the archive in conforming to the specification.

- bpo-28321: Fixed writing non-BMP characters with binary format in plistlib.

- bpo-28322: Fixed possible crashes when unpickle itertools objects from incorrect pickle data. Based on patch by John Leitch.

- Fix possible integer overflows and crashes in the mmap module with unusual usage patterns.

- bpo-1703178: Fix the ability to pass the –link-objects option to the distutils build_ext command.

- bpo-28253: Fixed calendar functions for extreme months: 0001-01 and 9999-12.

  Methods itermonthdays() and itermonthdays2() are reimplemented so that they don’t call itermonthdates() which can cause datetime.date under/overflow.

- bpo-28275: Fixed possible use after free in the decompress() methods of the LZMADecompressor and BZ2Decompressor classes. Original patch by John Leitch.

- bpo-27897: Fixed possible crash in sqlite3.Connection.create_collation() if pass invalid string-like object as a name. Patch by Xiang Zhang.

- bpo-18893: Fix invalid exception handling in Lib/ctypes/macholib/dyld.py. Patch by Madison May.

- bpo-27611: Fixed support of default root window in the tkinter.tix module.

- bpo-27348: In the traceback module, restore the formatting of exception messages like “Exception: None”. This fixes a regression introduced in 3.5a2.

- bpo-25651: Allow falsy values to be used for msg parameter of subTest().

- bpo-27932: Prevent memory leak in win32_ver().

- Fix UnboundLocalError in socket._sendfile_use_sendfile.

- bpo-28075: Check for ERROR_ACCESS_DENIED in Windows implementation of os.stat(). Patch by Eryk Sun.

- bpo-25270: Prevent codecs.escape_encode() from raising SystemError when an empty bytestring is passed.

- bpo-28181: Get antigravity over HTTPS. Patch by Kaartic Sivaraam.

- bpo-25895: Enable WebSocket URL schemes in urllib.parse.urljoin. Patch by Gergely Imreh and Markus Holtermann.

- bpo-27599: Fixed buffer overrun in binascii.b2a_qp() and binascii.a2b_qp().

- bpo-19003: m email.generator now replaces only `\r` and/or `\n` line endings, per the RFC, instead of all unicode line endings.

- bpo-28019: itertools.count() no longer rounds non-integer step in range between 1.0 and 2.0 to 1.

- bpo-25969: Update the lib2to3 grammar to handle the unpacking generalizations added in 3.5.

- bpo-14977: mailcap now respects the order of the lines in the mailcap files (“first match”), as required by RFC 1542. Patch by Michael Lazar.

- bpo-24594: Validates persist parameter when opening MSI database

- bpo-17582: xml.etree.ElementTree nows preserves whitespaces in attributes (Patch by Duane Griffin. Reviewed and approved by Stefan Behnel.)

- bpo-28047: Fixed calculation of line length used for the base64 CTE in the new email policies.

- bpo-27445: Don’t pass str(_charset) to MIMEText.set_payload(). Patch by Claude Paroz.

- bpo-22450: urllib now includes an `Accept: */*` header among the default headers. This makes the results of REST API requests more consistent and predictable especially when proxy servers are involved.

- lib2to3.pgen3.driver.load_grammar() now creates a stable cache file between runs given the same Grammar.txt input regardless of the hash randomization setting.

- bpo-27570: Avoid zero-length memcpy() etc calls with null source pointers in the “ctypes” and “array” modules.

- bpo-22233: Break email header lines only on the RFC specified CR and LF characters, not on arbitrary unicode line breaks. This also fixes a bug in HTTP header parsing.

- bpo-27988: Fix email iter_attachments incorrect mutation of payload list.

- bpo-27691: Fix ssl module’s parsing of GEN_RID subject alternative name fields in X.509 certs.

- bpo-27850: Remove 3DES from ssl module’s default cipher list to counter measure sweet32 attack (CVE-2016-2183).

- bpo-27766: Add ChaCha20 Poly1305 to ssl module’s default cipher list. (Required OpenSSL 1.1.0 or LibreSSL).

- bpo-26470: Port ssl and hashlib module to OpenSSL 1.1.0.

- Remove support for passing a file descriptor to os.access. It never worked but previously didn’t raise.

- bpo-12885: Fix error when distutils encounters symlink.

- bpo-27881: Fixed possible bugs when setting sqlite3.Connection.isolation_level. Based on patch by Xiang Zhang.

- bpo-27861: Fixed a crash in sqlite3.Connection.cursor() when a factory creates not a cursor. Patch by Xiang Zhang.

- bpo-19884: Avoid spurious output on OS X with Gnu Readline.

- bpo-27706: Restore deterministic behavior of random.Random().seed() for string seeds using seeding version 1. Allows sequences of calls to random() to exactly match those obtained in Python 2. Patch by Nofar Schnider.

- bpo-10513: Fix a regression in Connection.commit(). Statements should not be reset after a commit.

- A new version of typing.py from https://github.com/python/typing: Collection (only for 3.6) (bpo-27598). Add FrozenSet to __all__ (upstream #261). Fix crash in _get_type_vars() (upstream #259). Remove the dict constraint in ForwardRef._eval_type (upstream #252).

- bpo-27539: Fix unnormalised `Fraction.__pow__` result in the case of negative exponent and negative base.

- bpo-21718: cursor.description is now available for queries using CTEs.

- bpo-2466: posixpath.ismount now correctly recognizes mount points which the user does not have permission to access.

- bpo-27773: Correct some memory management errors server_hostname in _ssl.wrap_socket().

- bpo-26750: unittest.mock.create_autospec() now works properly for subclasses of property() and other data descriptors.

- In the curses module, raise an error if window.getstr() or window.instr() is passed a negative value.

- bpo-27783: Fix possible usage of uninitialized memory in operator.methodcaller.

- bpo-27774: Fix possible Py_DECREF on unowned object in _sre.

- bpo-27760: Fix possible integer overflow in binascii.b2a_qp.

- bpo-27758: Fix possible integer overflow in the _csv module for large record lengths.

- bpo-27568: Prevent HTTPoxy attack (CVE-2016-1000110). Ignore the HTTP_PROXY variable when REQUEST_METHOD environment is set, which indicates that the script is in CGI mode.

- bpo-27656: Do not assume sched.h defines any SCHED_* constants.

- bpo-27130: In the “zlib” module, fix handling of large buffers (typically 4 GiB) when compressing and decompressing. Previously, inputs were limited to 4 GiB, and compression and decompression operations did not properly handle results of 4 GiB.

- bpo-27533: Release GIL in nt._isdir

- bpo-17711: Fixed unpickling by the persistent ID with protocol 0. Original patch by Alexandre Vassalotti.

- bpo-27522: Avoid an unintentional reference cycle in email.feedparser.

- bpo-26844: Fix error message for imp.find_module() to refer to ‘path’ instead of ‘name’. Patch by Lev Maximov.

- bpo-23804: Fix SSL zero-length recv() calls to not block and not raise an error about unclean EOF.

- bpo-27466: Change time format returned by http.cookie.time2netscape, confirming the netscape cookie format and making it consistent with documentation.

- bpo-26664: Fix activate.fish by removing mis-use of `$`.

- bpo-22115: Fixed tracing Tkinter variables: trace_vdelete() with wrong mode no longer break tracing, trace_vinfo() now always returns a list of pairs of strings, tracing in the “u” mode now works.

- Fix a scoping issue in importlib.util.LazyLoader which triggered an UnboundLocalError when lazy-loading a module that was already put into sys.modules.

- bpo-27079: Fixed curses.ascii functions isblank(), iscntrl() and ispunct().

- bpo-26754: Some functions (compile() etc) accepted a filename argument encoded as an iterable of integers. Now only strings and byte-like objects are accepted.

- bpo-27048: Prevents distutils failing on Windows when environment variables contain non-ASCII characters

- bpo-27330: Fixed possible leaks in the ctypes module.

- bpo-27238: Got rid of bare excepts in the turtle module. Original patch by Jelle Zijlstra.

- bpo-27122: When an exception is raised within the context being managed by a contextlib.ExitStack() and one of the exit stack generators catches and raises it in a chain, do not re-raise the original exception when exiting, let the new chained one through. This avoids the PEP 479 bug described in issue25782.

### Security

- bpo-27278: Fix os.urandom() implementation using getrandom() on Linux. Truncate size to INT_MAX and loop until we collected enough random bytes, instead of casting a directly Py_ssize_t to int.

### Library

- bpo-26386: Fixed ttk.TreeView selection operations with item id’s containing spaces.

### Security

- bpo-22636: Avoid shell injection problems with ctypes.util.find_library().

### Library

- bpo-16182: Fix various functions in the “readline” module to use the locale encoding, and fix get_begidx() and get_endidx() to return code point indexes.
- bpo-27392: Add loop.connect_accepted_socket(). Patch by Jim Fulton.
- bpo-27930: Improved behaviour of logging.handlers.QueueListener. Thanks to Paulo Andrade and Petr Viktorin for the analysis and patch.
- bpo-21201: Improves readability of multiprocessing error message. Thanks to Wojciech Walczak for patch.
- bpo-27456: asyncio: Set TCP_NODELAY by default.
- bpo-27906: Fix socket accept exhaustion during high TCP traffic. Patch by Kevin Conway.
- bpo-28174: Handle when SO_REUSEPORT isn’t properly supported. Patch by Seth Michael Larson.
- bpo-26654: Inspect functools.partial in asyncio.Handle.__repr__. Patch by iceboy.
- bpo-26909: Fix slow pipes IO in asyncio. Patch by INADA Naoki.
- bpo-28176: Fix callbacks race in asyncio.SelectorLoop.sock_connect.
- bpo-27759: Fix selectors incorrectly retain invalid file descriptors. Patch by Mark Williams.
- bpo-28368: Refuse monitoring processes if the child watcher has no loop attached. Patch by Vincent Michel.
- bpo-28369: Raise RuntimeError when transport’s FD is used with add_reader, add_writer, etc.
- bpo-28370: Speedup asyncio.StreamReader.readexactly. Patch by Коренберг Марк.
- bpo-28371: Deprecate passing asyncio.Handles to run_in_executor.
- bpo-28372: Fix asyncio to support formatting of non-python coroutines.
- bpo-28399: Remove UNIX socket from FS before binding. Patch by Коренберг Марк.
- bpo-27972: Prohibit Tasks to await on themselves.
- bpo-26923: Fix asyncio.Gather to refuse being cancelled once all children are done. Patch by Johannes Ebke.
- bpo-26796: Don’t configure the number of workers for default threadpool executor. Initial patch by Hans Lawrenz.
- bpo-28600: Optimize loop.call_soon().
- bpo-28613: Fix get_event_loop() return the current loop if called from coroutines/callbacks.
- bpo-28639: Fix inspect.isawaitable to always return bool Patch by Justin Mayfield.
- bpo-28652: Make loop methods reject socket kinds they do not support.
- bpo-28653: Fix a refleak in functools.lru_cache.
- bpo-28703: Fix asyncio.iscoroutinefunction to handle Mock objects.
- bpo-24142: Reading a corrupt config file left the parser in an invalid state. Original patch by Florian Höch.
- bpo-28990: Fix SSL hanging if connection is closed before handshake completed. (Patch by HoHo-Ho)

### IDLE

- bpo-15308: Add ‘interrupt execution’ (^C) to Shell menu. Patch by Roger Serwy, updated by Bayard Randel.
- bpo-27922: Stop IDLE tests from ‘flashing’ gui widgets on the screen.
- Add version to title of IDLE help window.
- bpo-25564: In section on IDLE – console differences, mention that using exec means that __builtins__ is defined for each statement.
- bpo-27714: text_textview and test_autocomplete now pass when re-run in the same process. This occurs when test_idle fails when run with the -w option but without -jn. Fix warning from test_config.
- bpo-25507: IDLE no longer runs buggy code because of its tkinter imports. Users must include the same imports required to run directly in Python.
- bpo-27452: add line counter and crc to IDLE configHandler test dump.
- bpo-27365: Allow non-ascii chars in IDLE NEWS.txt, for contributor names.
- bpo-27245: IDLE: Cleanly delete custom themes and key bindings. Previously, when IDLE was started from a console or by import, a cascade of warnings was emitted. Patch by Serhiy Storchaka.

### C API

- bpo-28808: PyUnicode_CompareWithASCIIString() now never raises exceptions.
- bpo-26754: PyUnicode_FSDecoder() accepted a filename argument encoded as an iterable of integers. Now only strings and bytes-like objects are accepted.

### Documentation

- bpo-28513: Documented command-line interface of zipfile.

### Tests

- bpo-28950: Disallow -j0 to be combined with -T/-l/-M in regrtest command line arguments.
- bpo-28666: Now test.support.rmtree is able to remove unwritable or unreadable directories.
- bpo-23839: Various caches now are cleared before running every test file.
- bpo-28409: regrtest: fix the parser of command line arguments.
- bpo-27787: Call gc.collect() before checking each test for “dangling threads”, since the dangling threads are weak references.
- bpo-27369: In test_pyexpat, avoid testing an error message detail that changed in Expat 2.2.0.

### Tools/Demos

- bpo-27952: Get Tools/scripts/fixcid.py working with Python 3 and the current “re” module, avoid invalid Python backslash escapes, and fix a bug parsing escaped C quote signs.
- bpo-27332: Fixed the type of the first argument of module-level functions generated by Argument Clinic. Patch by Petr Viktorin.
- bpo-27418: Fixed Tools/importbench/importbench.py.

### Windows

- bpo-28251: Improvements to help manuals on Windows.
- bpo-28110: launcher.msi has different product codes between 32-bit and 64-bit
- bpo-25144: Ensures TargetDir is set before continuing with custom install.
- bpo-27469: Adds a shell extension to the launcher so that drag and drop works correctly.
- bpo-27309: Enabled proper Windows styles in python[w].exe manifest.

### Build

- bpo-29080: Removes hard dependency on hg.exe from PCBuild/build.bat
- bpo-23903: Added missed names to PC/python3.def.
- bpo-10656: Fix out-of-tree building on AIX. Patch by Tristan Carel and Michael Haubenwallner.
- bpo-26359: Rename –with-optimiations to –enable-optimizations.
- bpo-28444: Fix missing extensions modules when cross compiling.
- bpo-28248: Update Windows build and OS X installers to use OpenSSL 1.0.2j.
- bpo-28258: Fixed build with Estonian locale (python-config and distclean targets in Makefile). Patch by Arfrever Frehtes Taifersar Arahesis.
- bpo-26661: setup.py now detects system libffi with multiarch wrapper.
- bpo-28066: Fix the logic that searches build directories for generated include files when building outside the source tree.
- bpo-15819: Remove redundant include search directory option for building outside the source tree.
- bpo-27566: Fix clean target in freeze makefile (patch by Lisa Roach)
- bpo-27705: Update message in validate_ucrtbase.py
- bpo-27983: Cause lack of llvm-profdata tool when using clang as required for PGO linking to be a configure time error rather than make time when –with-optimizations is enabled. Also improve our ability to find the llvm-profdata tool on MacOS and some Linuxes.
- bpo-26307: The profile-opt build now applies PGO to the built-in modules.
- bpo-26359: Add the –with-optimizations configure flag.
- bpo-27713: Suppress spurious build warnings when updating importlib’s bootstrap files. Patch by Xiang Zhang
- bpo-25825: Correct the references to Modules/python.exp and ld_so_aix, which are required on AIX. This updates references to an installation path that was changed in 3.2a4, and undoes changed references to the build tree that were made in 3.5.0a1.
- bpo-27453: CPP invocation in configure must use CPPFLAGS. Patch by Chi Hsuan Yen.
- bpo-27641: The configure script now inserts comments into the makefile to prevent the pgen and _freeze_importlib executables from being cross-compiled.
- bpo-26662: Set PYTHON_FOR_GEN in configure as the Python program to be used for file generation during the build.
- bpo-10910: Avoid C++ compilation errors on FreeBSD and OS X. Also update FreedBSD version checks for the original ctype UTF-8 workaround.
- bpo-28676: Prevent missing ‘getentropy’ declaration warning on macOS. Patch by Gareth Rees.

## Python 3.5.2 final

Release date: 2016-06-26

### Core and Builtins

- bpo-26930: Update Windows builds to use OpenSSL 1.0.2h.

### Tests

- bpo-26867: Ubuntu’s openssl OP_NO_SSLv3 is forced on by default; fix test.

### IDLE

- bpo-27365: Allow non-ascii in idlelib/NEWS.txt - minimal part for 3.5.2.

## Python 3.5.2 release candidate 1

Release date: 2016-06-12

### Core and Builtins

- bpo-27066: Fixed SystemError if a custom opener (for open()) returns a negative number without setting an exception.
- bpo-20041: Fixed TypeError when frame.f_trace is set to None. Patch by Xavier de Gaye.
- bpo-26168: Fixed possible refleaks in failing Py_BuildValue() with the “N” format unit.
- bpo-26991: Fix possible refleak when creating a function with annotations.
- bpo-27039: Fixed bytearray.remove() for values greater than 127. Patch by Joe Jevnik.
- bpo-23640: int.from_bytes() no longer bypasses constructors for subclasses.
- bpo-26811: gc.get_objects() no longer contains a broken tuple with NULL pointer.
- bpo-20120: Use RawConfigParser for .pypirc parsing, removing support for interpolation unintentionally added with move to Python 3. Behavior no longer does any interpolation in .pypirc files, matching behavior in Python 2.7 and Setuptools 19.0.
- bpo-26659: Make the builtin slice type support cycle collection.
- bpo-26718: super.__init__ no longer leaks memory if called multiple times. NOTE: A direct call of super.__init__ is not endorsed!
- bpo-25339: PYTHONIOENCODING now has priority over locale in setting the error handler for stdin and stdout.
- bpo-26494: Fixed crash on iterating exhausting iterators. Affected classes are generic sequence iterators, iterators of str, bytes, bytearray, list, tuple, set, frozenset, dict, OrderedDict, corresponding views and os.scandir() iterator.
- bpo-26581: If coding cookie is specified multiple times on a line in Python source code file, only the first one is taken to account.
- bpo-26464: Fix str.translate() when string is ASCII and first replacements removes character, but next replacement uses a non-ASCII character or a string longer than 1 character. Regression introduced in Python 3.5.0.
- bpo-22836: Ensure exception reports from PyErr_Display() and PyErr_WriteUnraisable() are sensible even when formatting them produces secondary errors. This affects the reports produced by sys.__excepthook__() and when __del__() raises an exception.
- bpo-26302: Correct behavior to reject comma as a legal character for cookie names.
- bpo-4806: Avoid masking the original TypeError exception when using star (`*`) unpacking in function calls. Based on patch by Hagen Fürstenau and Daniel Urban.
- bpo-27138: Fix the doc comment for FileFinder.find_spec().
- bpo-26154: Add a new private _PyThreadState_UncheckedGet() function to get the current Python thread state, but don’t issue a fatal error if it is NULL. This new function must be used instead of accessing directly the _PyThreadState_Current variable. The variable is no more exposed since Python 3.5.1 to hide the exact implementation of atomic C types, to avoid compiler issues.
- bpo-26194: Deque.insert() gave odd results for bounded deques that had reached their maximum size. Now an IndexError will be raised when attempting to insert into a full deque.
- bpo-25843: When compiling code, don’t merge constants if they are equal but have a different types. For example, `f1, f2 = lambda: 1, lambda: 1.0` is now correctly compiled to two different functions: `f1()` returns `1` (`int`) and `f2()` returns `1.0` (`int`), even if `1` and `1.0` are equal.
- bpo-22995: [UPDATE] Comment out the one of the pickleability tests in _PyObject_GetState() due to regressions observed in Cython-based projects.
- bpo-25961: Disallowed null characters in the type name.
- bpo-25973: Fix segfault when an invalid nonlocal statement binds a name starting with two underscores.
- bpo-22995: Instances of extension types with a state that aren’t subclasses of list or dict and haven’t implemented any pickle-related methods (__reduce__, __reduce_ex__, __getnewargs__, __getnewargs_ex__, or __getstate__), can no longer be pickled. Including memoryview.
- bpo-20440: Massive replacing unsafe attribute setting code with special macro Py_SETREF.
- bpo-25766: Special method __bytes__() now works in str subclasses.
- bpo-25421: __sizeof__ methods of builtin types now use dynamic basic size. This allows sys.getsize() to work correctly with their subclasses with __slots__ defined.
- bpo-25709: Fixed problem with in-place string concatenation and utf-8 cache.
- bpo-27147: Mention PEP 420 in the importlib docs.
- bpo-24097: Fixed crash in object.__reduce__() if slot name is freed inside __getattr__.
- bpo-24731: Fixed crash on converting objects with special methods __bytes__, __trunc__, and __float__ returning instances of subclasses of bytes, int, and float to subclasses of bytes, int, and float correspondingly.
- bpo-26478: Fix semantic bugs when using binary operators with dictionary views and tuples.
- bpo-26171: Fix possible integer overflow and heap corruption in zipimporter.get_data().
- bpo-25660: Fix TAB key behaviour in REPL with readline.
- bpo-25887: Raise a RuntimeError when a coroutine object is awaited more than once.
- bpo-27243: Update the __aiter__ protocol: instead of returning an awaitable that resolves to an asynchronous iterator, the asynchronous iterator should be returned directly. Doing the former will trigger a PendingDeprecationWarning.

### Security

- bpo-26556: Update expat to 2.1.1, fixes CVE-2015-1283.
- Fix TLS stripping vulnerability in smtplib, CVE-2016-0772. Reported by Team Oststrom

### Library

- bpo-21386: Implement missing IPv4Address.is_global property. It was documented since 07a5610bae9d. Initial patch by Roger Luethi.
- bpo-20900: distutils register command now decodes HTTP responses correctly. Initial patch by ingrid.
- A new version of typing.py provides several new classes and features: @overload outside stubs, Reversible, DefaultDict, Text, ContextManager, Type[], NewType(), TYPE_CHECKING, and numerous bug fixes (note that some of the new features are not yet implemented in mypy or other static analyzers). Also classes for PEP 492 (Awaitable, AsyncIterable, AsyncIterator) have been added (in fact they made it into 3.5.1 but were never mentioned).
- bpo-25738: Stop http.server.BaseHTTPRequestHandler.send_error() from sending a message body for 205 Reset Content. Also, don’t send Content header fields in responses that don’t have a body. Patch by Susumu Koshiba.
- bpo-21313: Fix the “platform” module to tolerate when sys.version contains truncated build information.

### Security

- bpo-26839: On Linux, `os.urandom()` now calls `getrandom()` with `GRND_NONBLOCK` to fall back on reading `/dev/urandom` if the urandom entropy pool is not initialized yet. Patch written by Colm Buckley.

### Library

- bpo-27164: In the zlib module, allow decompressing raw Deflate streams with a predefined zdict. Based on patch by Xiang Zhang.

- bpo-24291: Fix wsgiref.simple_server.WSGIRequestHandler to completely write data to the client. Previously it could do partial writes and truncate data. Also, wsgiref.handler.ServerHandler can now handle stdout doing partial writes, but this is deprecated.

- bpo-26809: Add `__all__` to `string`. Patch by Emanuel Barry.

- bpo-26373: subprocess.Popen.communicate now correctly ignores BrokenPipeError when the child process dies before .communicate() is called in more/all circumstances.

- bpo-21776: distutils.upload now correctly handles HTTPError. Initial patch by Claudiu Popa.

- bpo-27114: Fix SSLContext._load_windows_store_certs fails with PermissionError

- bpo-18383: Avoid creating duplicate filters when using filterwarnings and simplefilter. Based on patch by Alex Shkop.

- bpo-27057: Fix os.set_inheritable() on Android, ioctl() is blocked by SELinux and fails with EACCESS. The function now falls back to fcntl(). Patch written by Michał Bednarski.

- bpo-27014: Fix infinite recursion using typing.py. Thanks to Kalle Tuure!

- bpo-14132: Fix urllib.request redirect handling when the target only has a query string. Original fix by Ján Janech.

- bpo-17214: The “urllib.request” module now percent-encodes non-ASCII bytes found in redirect target URLs. Some servers send Location header fields with non-ASCII bytes, but “http.client” requires the request target to be ASCII-encodable, otherwise a UnicodeEncodeError is raised. Based on patch by Christian Heimes.

- bpo-26892: Honor debuglevel flag in urllib.request.HTTPHandler. Patch contributed by Chi Hsuan Yen.

- bpo-22274: In the subprocess module, allow stderr to be redirected to stdout even when stdout is not redirected. Patch by Akira Li.

- bpo-26807: mock_open ‘files’ no longer error on readline at end of file. Patch from Yolanda Robla.

- bpo-25745: Fixed leaking a userptr in curses panel destructor.

- bpo-26977: Removed unnecessary, and ignored, call to sum of squares helper in statistics.pvariance.

- bpo-26881: The modulefinder module now supports extended opcode arguments.

- bpo-23815: Fixed crashes related to directly created instances of types in _tkinter and curses.panel modules.

- bpo-17765: weakref.ref() no longer silently ignores keyword arguments. Patch by Georg Brandl.

- bpo-26873: xmlrpc now raises ResponseError on unsupported type tags instead of silently return incorrect result.

- bpo-26711: Fixed the comparison of plistlib.Data with other types.

- bpo-24114: Fix an uninitialized variable in `ctypes.util`.

  The bug only occurs on SunOS when the ctypes implementation searches for the `crle` program. Patch by Xiang Zhang. Tested on SunOS by Kees Bos.

- bpo-26864: In urllib.request, change the proxy bypass host checking against no_proxy to be case-insensitive, and to not match unrelated host names that happen to have a bypassed hostname as a suffix. Patch by Xiang Zhang.

- bpo-26634: recursive_repr() now sets __qualname__ of wrapper. Patch by Xiang Zhang.

- bpo-26804: urllib.request will prefer lower_case proxy environment variables over UPPER_CASE or Mixed_Case ones. Patch contributed by Hans-Peter Jansen.

- bpo-26837: assertSequenceEqual() now correctly outputs non-stringified differing items (like bytes in the -b mode). This affects assertListEqual() and assertTupleEqual().

- bpo-26041: Remove “will be removed in Python 3.7” from deprecation messages of platform.dist() and platform.linux_distribution(). Patch by Kumaripaba Miyurusara Athukorala.

- bpo-26822: itemgetter, attrgetter and methodcaller objects no longer silently ignore keyword arguments.

- bpo-26733: Disassembling a class now disassembles class and static methods. Patch by Xiang Zhang.

- bpo-26801: Fix error handling in `shutil.get_terminal_size()`, catch `AttributeError` instead of `NameError`. Patch written by Emanuel Barry.

- bpo-24838: tarfile’s ustar and gnu formats now correctly calculate name and link field limits for multibyte character encodings like utf-8.

### Security

- bpo-26657: Fix directory traversal vulnerability with http.server on Windows. This fixes a regression that was introduced in 3.3.4rc1 and 3.4.0rc1. Based on patch by Philipp Hagemeister.

### Library

- bpo-26717: Stop encoding Latin-1-ized WSGI paths with UTF-8. Patch by Anthony Sottile.
- bpo-26735: Fix `os.urandom()` on Solaris 11.3 and newer when reading more than 1,024 bytes: call `getrandom()` multiple times with a limit of 1024 bytes per call.
- bpo-16329: Add .webm to mimetypes.types_map. Patch by Giampaolo Rodola’.
- bpo-13952: Add .csv to mimetypes.types_map. Patch by Geoff Wilson.
- bpo-26709: Fixed Y2038 problem in loading binary PLists.
- bpo-23735: Handle terminal resizing with Readline 6.3+ by installing our own SIGWINCH handler. Patch by Eric Price.
- bpo-26586: In http.server, respond with “413 Request header fields too large” if there are too many header fields to parse, rather than killing the connection and raising an unhandled exception. Patch by Xiang Zhang.
- bpo-22854: Change BufferedReader.writable() and BufferedWriter.readable() to always return False.
- bpo-25195: Fix a regression in mock.MagicMock. _Call is a subclass of tuple (changeset 3603bae63c13 only works for classes) so we need to implement __ne__ ourselves. Patch by Andrew Plummer.
- bpo-26644: Raise ValueError rather than SystemError when a negative length is passed to SSLSocket.recv() or read().
- bpo-23804: Fix SSL recv(0) and read(0) methods to return zero bytes instead of up to 1024.
- bpo-26616: Fixed a bug in datetime.astimezone() method.
- bpo-21925: `warnings.formatwarning()` now catches exceptions on `linecache.getline(...)` to be able to log `ResourceWarning` emitted late during the Python shutdown process.
- bpo-24266: Ctrl+C during Readline history search now cancels the search mode when compiled with Readline 7.
- bpo-26560: Avoid potential ValueError in BaseHandler.start_response. Initial patch by Peter Inglesby.

### Security

- bpo-26313: ssl.py _load_windows_store_certs fails if windows cert store is empty. Patch by Baji.

### Library

- bpo-26569: Fix `pyclbr.readmodule()` and `pyclbr.readmodule_ex()` to support importing packages.
- bpo-26499: Account for remaining Content-Length in HTTPResponse.readline() and read1(). Based on patch by Silent Ghost. Also document that HTTPResponse now supports these methods.
- bpo-25320: Handle sockets in directories unittest discovery is scanning. Patch from Victor van den Elzen.
- bpo-16181: cookiejar.http2time() now returns None if year is higher than datetime.MAXYEAR.
- bpo-26513: Fixes platform module detection of Windows Server
- bpo-23718: Fixed parsing time in week 0 before Jan 1. Original patch by Tamás Bence Gedai.
- bpo-20589: Invoking Path.owner() and Path.group() on Windows now raise NotImplementedError instead of ImportError.
- bpo-26177: Fixed the keys() method for Canvas and Scrollbar widgets.
- bpo-15068: Got rid of excessive buffering in the fileinput module. The bufsize parameter is no longer used.
- bpo-2202: Fix UnboundLocalError in AbstractDigestAuthHandler.get_algorithm_impls. Initial patch by Mathieu Dupuy.
- bpo-25718: Fixed pickling and copying the accumulate() iterator with total is None.
- bpo-26475: Fixed debugging output for regular expressions with the (?x) flag.
- bpo-26457: Fixed the subnets() methods in IP network classes for the case when resulting prefix length is equal to maximal prefix length. Based on patch by Xiang Zhang.
- bpo-26385: Remove the file if the internal open() call in NamedTemporaryFile() fails. Patch by Silent Ghost.
- bpo-26402: Fix XML-RPC client to retry when the server shuts down a persistent connection. This was a regression related to the new http.client.RemoteDisconnected exception in 3.5.0a4.
- bpo-25913: Leading `<~` is optional now in base64.a85decode() with adobe=True. Patch by Swati Jaiswal.
- bpo-26186: Remove an invalid type check in importlib.util.LazyLoader.
- bpo-26367: importlib.__import__() raises SystemError like builtins.__import__() when `level` is specified but without an accompanying package specified.
- bpo-26309: In the “socketserver” module, shut down the request (closing the connected socket) when verify_request() returns false. Patch by Aviv Palivoda.

### Security

- bpo-25939: On Windows open the cert store readonly in ssl.enum_certificates.

### Library

- bpo-25995: os.walk() no longer uses FDs proportional to the tree depth.
- bpo-26117: The os.scandir() iterator now closes file descriptor not only when the iteration is finished, but when it was failed with error.
- bpo-25911: Restored support of bytes paths in os.walk() on Windows.
- bpo-26045: Add UTF-8 suggestion to error message when posting a non-Latin-1 string with http.client.
- bpo-12923: Reset FancyURLopener’s redirect counter even if there is an exception. Based on patches by Brian Brazil and Daniel Rocco.
- bpo-25945: Fixed a crash when unpickle the functools.partial object with wrong state. Fixed a leak in failed functools.partial constructor. “args” and “keywords” attributes of functools.partial have now always types tuple and dict correspondingly.
- bpo-26202: copy.deepcopy() now correctly copies range() objects with non-atomic attributes.
- bpo-23076: Path.glob() now raises a ValueError if it’s called with an invalid pattern. Patch by Thomas Nyberg.
- bpo-19883: Fixed possible integer overflows in zipimport.
- bpo-26227: On Windows, getnameinfo(), gethostbyaddr() and gethostbyname_ex() functions of the socket module now decode the hostname from the ANSI code page rather than UTF-8.
- bpo-26147: xmlrpc now works with strings not encodable with used non-UTF-8 encoding.
- bpo-25935: Garbage collector now breaks reference loops with OrderedDict.
- bpo-16620: Fixed AttributeError in msilib.Directory.glob().
- bpo-26013: Added compatibility with broken protocol 2 pickles created in old Python 3 versions (3.4.3 and lower).
- bpo-25850: Use cross-compilation by default for 64-bit Windows.
- bpo-17633: Improve zipimport’s support for namespace packages.
- bpo-24705: Fix sysconfig._parse_makefile not expanding ${} vars appearing before $() vars.
- bpo-22138: Fix mock.patch behavior when patching descriptors. Restore original values after patching. Patch contributed by Sean McCully.
- bpo-25672: In the ssl module, enable the SSL_MODE_RELEASE_BUFFERS mode option if it is safe to do so.
- bpo-26012: Don’t traverse into symlinks for `**` pattern in pathlib.Path.[r]glob().
- bpo-24120: Ignore PermissionError when traversing a tree with pathlib.Path.[r]glob(). Patch by Ulrich Petri.
- bpo-25447: fileinput now uses sys.stdin as-is if it does not have a buffer attribute (restores backward compatibility).
- bpo-25447: Copying the lru_cache() wrapper object now always works, independently from the type of the wrapped object (by returning the original object unchanged).
- bpo-24103: Fixed possible use after free in ElementTree.XMLPullParser.
- bpo-25860: os.fwalk() no longer skips remaining directories when error occurs. Original patch by Samson Lee.
- bpo-25914: Fixed and simplified OrderedDict.__sizeof__.
- bpo-25902: Fixed various refcount issues in ElementTree iteration.
- bpo-25717: Restore the previous behaviour of tolerating most fstat() errors when opening files. This was a regression in 3.5a1, and stopped anonymous temporary files from working in special cases.
- bpo-24903: Fix regression in number of arguments compileall accepts when ‘-d’ is specified. The check on the number of arguments has been dropped completely as it never worked correctly anyway.
- bpo-25764: In the subprocess module, preserve any exception caused by fork() failure when preexec_fn is used.
- bpo-6478: _strptime’s regexp cache now is reset after changing timezone with time.tzset().
- bpo-14285: When executing a package with the “python -m package” option, and package initialization fails, a proper traceback is now reported. The “runpy” module now lets exceptions from package initialization pass back to the caller, rather than raising ImportError.
- bpo-19771: Also in runpy and the “-m” option, omit the irrelevant message “… is a package and cannot be directly executed” if the package could not even be initialized (e.g. due to a bad `*.pyc` file).
- bpo-25177: Fixed problem with the mean of very small and very large numbers. As a side effect, statistics.mean and statistics.variance should be significantly faster.
- bpo-25718: Fixed copying object with state with boolean value is false.
- bpo-10131: Fixed deep copying of minidom documents. Based on patch by Marian Ganisin.
- bpo-25725: Fixed a reference leak in pickle.loads() when unpickling invalid data including tuple instructions.
- bpo-25663: In the Readline completer, avoid listing duplicate global names, and search the global namespace before searching builtins.
- bpo-25688: Fixed file leak in ElementTree.iterparse() raising an error.
- bpo-23914: Fixed SystemError raised by unpickler on broken pickle data.
- bpo-25691: Fixed crash on deleting ElementTree.Element attributes.
- bpo-25624: ZipFile now always writes a ZIP_STORED header for directory entries. Patch by Dingyuan Wang.
- Skip getaddrinfo if host is already resolved. Patch by A. Jesse Jiryu Davis.
- bpo-26050: Add asyncio.StreamReader.readuntil() method. Patch by Марк Коренберг.
- bpo-25924: Avoid unnecessary serialization of getaddrinfo(3) calls on OS X versions 10.5 or higher. Original patch by A. Jesse Jiryu Davis.
- bpo-26406: Avoid unnecessary serialization of getaddrinfo(3) calls on current versions of OpenBSD and NetBSD. Patch by A. Jesse Jiryu Davis.
- bpo-26848: Fix asyncio/subprocess.communicate() to handle empty input. Patch by Jack O’Connor.
- bpo-27040: Add loop.get_exception_handler method
- bpo-27041: asyncio: Add loop.create_future method
- bpo-27223: asyncio: Fix _read_ready and _write_ready to respect _conn_lost. Patch by Łukasz Langa.
- bpo-22970: asyncio: Fix inconsistency cancelling Condition.wait. Patch by David Coles.

### IDLE

- bpo-5124: Paste with text selected now replaces the selection on X11. This matches how paste works on Windows, Mac, most modern Linux apps, and ttk widgets. Original patch by Serhiy Storchaka.
- bpo-24759: Make clear in idlelib.idle_test.__init__ that the directory is a private implementation of test.test_idle and tool for maintainers.
- bpo-27196: Stop ‘ThemeChanged’ warnings when running IDLE tests. These persisted after other warnings were suppressed in #20567. Apply Serhiy Storchaka’s update_idletasks solution to four test files. Record this additional advice in idle_test/README.txt
- bpo-20567: Revise idle_test/README.txt with advice about avoiding tk warning messages from tests. Apply advice to several IDLE tests.
- bpo-27117: Make colorizer htest and turtledemo work with dark themes. Move code for configuring text widget colors to a new function.
- bpo-26673: When tk reports font size as 0, change to size 10. Such fonts on Linux prevented the configuration dialog from opening.
- bpo-21939: Add test for IDLE’s percolator. Original patch by Saimadhav Heblikar.
- bpo-21676: Add test for IDLE’s replace dialog. Original patch by Saimadhav Heblikar.
- bpo-18410: Add test for IDLE’s search dialog. Original patch by Westley Martínez.
- bpo-21703: Add test for IDLE’s undo delegator. Original patch by Saimadhav Heblikar .
- bpo-27044: Add ConfigDialog.remove_var_callbacks to stop memory leaks.
- bpo-23977: Add more asserts to test_delegator.
- bpo-20640: Add tests for idlelib.configHelpSourceEdit. Patch by Saimadhav Heblikar.
- In the ‘IDLE-console differences’ section of the IDLE doc, clarify how running with IDLE affects sys.modules and the standard streams.
- bpo-25507: fix incorrect change in IOBinding that prevented printing. Augment IOBinding htest to include all major IOBinding functions.
- bpo-25905: Revert unwanted conversion of ‘ to ’ RIGHT SINGLE QUOTATION MARK in README.txt and open this and NEWS.txt with ‘ascii’. Re-encode CREDITS.txt to utf-8 and open it with ‘utf-8’.

### Documentation

- bpo-19489: Moved the search box from the sidebar to the header and footer of each page. Patch by Ammar Askar.
- bpo-24136: Document the new PEP 448 unpacking syntax of 3.5.
- bpo-26736: Used HTTPS for external links in the documentation if possible.
- bpo-6953: Rework the Readline module documentation to group related functions together, and add more details such as what underlying Readline functions and variables are accessed.
- bpo-23606: Adds note to ctypes documentation regarding cdll.msvcrt.
- bpo-25500: Fix documentation to not claim that __import__ is searched for in the global scope.
- bpo-26014: Update 3.x packaging documentation: * “See also” links to the new docs are now provided in the legacy pages * links to setuptools documentation have been updated

### Tests

- bpo-21916: Added tests for the turtle module. Patch by ingrid, Gregory Loyse and Jelle Zijlstra.
- bpo-26523: The multiprocessing thread pool (multiprocessing.dummy.Pool) was untested.
- bpo-26015: Added new tests for pickling iterators of mutable sequences.
- bpo-26325: Added test.support.check_no_resource_warning() to check that no ResourceWarning is emitted.
- bpo-25940: Changed test_ssl to use self-signed.pythontest.net. This avoids relying on svn.python.org, which recently changed root certificate.
- bpo-25616: Tests for OrderedDict are extracted from test_collections into separate file test_ordered_dict.
- bpo-26583: Skip test_timestamp_overflow in test_import if bytecode files cannot be written.

### Build

- bpo-26884: Fix linking extension modules for cross builds. Patch by Xavier de Gaye.
- bpo-22359: Disable the rules for running _freeze_importlib and pgen when cross-compiling. The output of these programs is normally saved with the source code anyway, and is still regenerated when doing a native build. Patch by Xavier de Gaye.
- bpo-27229: Fix the cross-compiling pgen rule for in-tree builds. Patch by Xavier de Gaye.
- bpo-21668: Link audioop, _datetime, _ctypes_test modules to libm, except on Mac OS X. Patch written by Xavier de Gaye.
- bpo-25702: A –with-lto configure option has been added that will enable link time optimizations at build time during a make profile-opt. Some compilers and toolchains are known to not produce stable code when using LTO, be sure to test things thoroughly before relying on it. It can provide a few % speed up over profile-opt alone.
- bpo-26624: Adds validation of ucrtbase[d].dll version with warning for old versions.
- bpo-17603: Avoid error about nonexistant fileblocks.o file by using a lower-level check for st_blocks in struct stat.
- bpo-26079: Fixing the build output folder for tix-8.4.3.6. Patch by Bjoern Thiel.
- bpo-26465: Update Windows builds to use OpenSSL 1.0.2g.
- bpo-24421: Compile Modules/_math.c once, before building extensions. Previously it could fail to compile properly if the math and cmath builds were concurrent.
- bpo-25348: Added `--pgo` and `--pgo-job` arguments to `PCbuild\build.bat` for building with Profile-Guided Optimization. The old `PCbuild\build_pgo.bat` script is now deprecated, and simply calls `PCbuild\build.bat --pgo %*`.
- bpo-25827: Add support for building with ICC to `configure`, including a new `--with-icc` flag.
- bpo-25696: Fix installation of Python on UNIX with make -j9.
- bpo-26930: Update OS X 10.5+ 32-bit-only installer to build and link with OpenSSL 1.0.2h.
- bpo-26268: Update Windows builds to use OpenSSL 1.0.2f.
- bpo-25136: Support Apple Xcode 7’s new textual SDK stub libraries.
- bpo-24324: Do not enable unreachable code warnings when using gcc as the option does not work correctly in older versions of gcc and has been silently removed as of gcc-4.5.

### Windows

- bpo-27053: Updates make_zip.py to correctly generate library ZIP file.
- bpo-26268: Update the prepare_ssl.py script to handle OpenSSL releases that don’t include the contents of the include directory (that is, 1.0.2e and later).
- bpo-26071: bdist_wininst created binaries fail to start and find 32bit Python
- bpo-26073: Update the list of magic numbers in launcher
- bpo-26065: Excludes venv from library when generating embeddable distro.

### Tools/Demos

- bpo-26799: Fix python-gdb.py: don’t get C types once when the Python code is loaded, but get C types on demand. The C types can change if python-gdb.py is loaded before the Python executable. Patch written by Thomas Ilsche.
- bpo-26271: Fix the Freeze tool to properly use flags passed through configure. Patch by Daniel Shaulov.
- bpo-26489: Add dictionary unpacking support to Tools/parser/unparse.py. Patch by Guo Ci Teo.
- bpo-26316: Fix variable name typo in Argument Clinic.

### Windows

- bpo-17500: Remove unused and outdated icons. (See also: https://github.com/python/pythondotorg/issues/945)

## Python 3.5.1 final

Release date: 2015-12-06

### Core and Builtins

- bpo-25709: Fixed problem with in-place string concatenation and utf-8 cache.

### Windows

- bpo-25715: Python 3.5.1 installer shows wrong upgrade path and incorrect logic for launcher detection.

## Python 3.5.1 release candidate 1

Release date: 2015-11-22

### Core and Builtins

- bpo-25630: Fix a possible segfault during argument parsing in functions that accept filesystem paths.
- bpo-23564: Fixed a partially broken sanity check in the _posixsubprocess internals regarding how fds_to_pass were passed to the child. The bug had no actual impact as subprocess.py already avoided it.
- bpo-25388: Fixed tokenizer crash when processing undecodable source code with a null byte.
- bpo-25462: The hash of the key now is calculated only once in most operations in C implementation of OrderedDict.
- bpo-22995: Default implementation of __reduce__ and __reduce_ex__ now rejects builtin types with not defined __new__.
- bpo-25555: Fix parser and AST: fill lineno and col_offset of “arg” node when compiling AST from Python objects.
- bpo-24802: Avoid buffer overreads when int(), float(), compile(), exec() and eval() are passed bytes-like objects. These objects are not necessarily terminated by a null byte, but the functions assumed they were.
- bpo-24726: Fixed a crash and leaking NULL in repr() of OrderedDict that was mutated by direct calls of dict methods.
- bpo-25449: Iterating OrderedDict with keys with unstable hash now raises KeyError in C implementations as well as in Python implementation.
- bpo-25395: Fixed crash when highly nested OrderedDict structures were garbage collected.
- bpo-25274: sys.setrecursionlimit() now raises a RecursionError if the new recursion limit is too low depending at the current recursion depth. Modify also the “lower-water mark” formula to make it monotonic. This mark is used to decide when the overflowed flag of the thread state is reset.
- bpo-24402: Fix input() to prompt to the redirected stdout when sys.stdout.fileno() fails.
- bpo-24806: Prevent builtin types that are not allowed to be subclassed from being subclassed through multiple inheritance.
- bpo-24848: Fixed a number of bugs in UTF-7 decoding of misformed data.
- bpo-25280: Import trace messages emitted in verbose (-v) mode are no longer formatted twice.
- bpo-25003: On Solaris 11.3 or newer, os.urandom() now uses the getrandom() function instead of the getentropy() function. The getentropy() function is blocking to generate very good quality entropy, os.urandom() doesn’t need such high-quality entropy.
- bpo-25182: The stdprinter (used as sys.stderr before the io module is imported at startup) now uses the backslashreplace error handler.
- bpo-25131: Make the line number and column offset of set/dict literals and comprehensions correspond to the opening brace.
- bpo-25150: Hide the private _Py_atomic_xxx symbols from the public Python.h header to fix a compilation error with OpenMP. PyThreadState_GET() becomes an alias to PyThreadState_Get() to avoid ABI incompatibilities.

### Library

- bpo-25626: Change three zlib functions to accept sizes that fit in Py_ssize_t, but internally cap those sizes to UINT_MAX. This resolves a regression in 3.5 where GzipFile.read() failed to read chunks larger than 2 or 4 GiB. The change affects the zlib.Decompress.decompress() max_length parameter, the zlib.decompress() bufsize parameter, and the zlib.Decompress.flush() length parameter.
- bpo-25583: Avoid incorrect errors raised by os.makedirs(exist_ok=True) when the OS gives priority to errors such as EACCES over EEXIST.
- bpo-25593: Change semantics of EventLoop.stop() in asyncio.
- bpo-6973: When we know a subprocess.Popen process has died, do not allow the send_signal(), terminate(), or kill() methods to do anything as they could potentially signal a different process.
- bpo-25590: In the Readline completer, only call getattr() once per attribute.
- bpo-25498: Fix a crash when garbage-collecting ctypes objects created by wrapping a memoryview. This was a regression made in 3.5a1. Based on patch by Eryksun.
- bpo-25584: Added “escape” to the __all__ list in the glob module.
- bpo-25584: Fixed recursive glob() with patterns starting with `**`.
- bpo-25446: Fix regression in smtplib’s AUTH LOGIN support.
- bpo-18010: Fix the pydoc web server’s module search function to handle exceptions from importing packages.
- bpo-25554: Got rid of circular references in regular expression parsing.
- bpo-25510: fileinput.FileInput.readline() now returns b’’ instead of ‘’ at the end if the FileInput was opened with binary mode. Patch by Ryosuke Ito.
- bpo-25503: Fixed inspect.getdoc() for inherited docstrings of properties. Original patch by John Mark Vandenberg.
- bpo-25515: Always use os.urandom as a source of randomness in uuid.uuid4.
- bpo-21827: Fixed textwrap.dedent() for the case when largest common whitespace is a substring of smallest leading whitespace. Based on patch by Robert Li.
- bpo-25447: The lru_cache() wrapper objects now can be copied and pickled (by returning the original object unchanged).
- bpo-25390: typing: Don’t crash on Union[str, Pattern].
- bpo-25441: asyncio: Raise error from drain() when socket is closed.
- bpo-25410: Cleaned up and fixed minor bugs in C implementation of OrderedDict.
- bpo-25411: Improved Unicode support in SMTPHandler through better use of the email package. Thanks to user simon04 for the patch.
- bpo-25407: Remove mentions of the formatter module being removed in Python 3.6.
- bpo-25406: Fixed a bug in C implementation of OrderedDict.move_to_end() that caused segmentation fault or hang in iterating after moving several items to the start of ordered dict.
- bpo-25364: zipfile now works in threads disabled builds.
- bpo-25328: smtpd’s SMTPChannel now correctly raises a ValueError if both decode_data and enable_SMTPUTF8 are set to true.
- bpo-25316: distutils raises OSError instead of DistutilsPlatformError when MSVC is not installed.
- bpo-25380: Fixed protocol for the STACK_GLOBAL opcode in pickletools.opcodes.
- bpo-23972: Updates asyncio datagram create method allowing reuseport and reuseaddr socket options to be set prior to binding the socket. Mirroring the existing asyncio create_server method the reuseaddr option for datagram sockets defaults to True if the O/S is ‘posix’ (except if the platform is Cygwin). Patch by Chris Laws.
- bpo-25304: Add asyncio.run_coroutine_threadsafe(). This lets you submit a coroutine to a loop from another thread, returning a concurrent.futures.Future. By Vincent Michel.
- bpo-25232: Fix CGIRequestHandler to split the query from the URL at the first question mark (?) rather than the last. Patch from Xiang Zhang.
- bpo-24657: Prevent CGIRequestHandler from collapsing slashes in the query part of the URL as if it were a path. Patch from Xiang Zhang.
- bpo-24483: C implementation of functools.lru_cache() now calculates key’s hash only once.
- bpo-22958: Constructor and update method of weakref.WeakValueDictionary now accept the self and the dict keyword arguments.
- bpo-22609: Constructor of collections.UserDict now accepts the self keyword argument.
- bpo-25111: Fixed comparison of traceback.FrameSummary.
- bpo-25262: Added support for BINBYTES8 opcode in Python implementation of unpickler. Highest 32 bits of 64-bit size for BINUNICODE8 and BINBYTES8 opcodes no longer silently ignored on 32-bit platforms in C implementation.
- bpo-25034: Fix string.Formatter problem with auto-numbering and nested format_specs. Patch by Anthon van der Neut.
- bpo-25233: Rewrite the guts of asyncio.Queue and asyncio.Semaphore to be more understandable and correct.
- bpo-25203: Failed readline.set_completer_delims() no longer left the module in inconsistent state.
- bpo-23600: Default implementation of tzinfo.fromutc() was returning wrong results in some cases.
- bpo-23329: Allow the ssl module to be built with older versions of LibreSSL.
- Prevent overflow in _Unpickler_Read.
- bpo-25047: The XML encoding declaration written by Element Tree now respects the letter case given by the user. This restores the ability to write encoding names in uppercase like “UTF-8”, which worked in Python 2.
- bpo-25135: Make deque_clear() safer by emptying the deque before clearing. This helps avoid possible reentrancy issues.
- bpo-19143: platform module now reads Windows version from kernel32.dll to avoid compatibility shims.
- bpo-25092: Fix datetime.strftime() failure when errno was already set to EINVAL.
- bpo-23517: Fix rounding in fromtimestamp() and utcfromtimestamp() methods of datetime.datetime: microseconds are now rounded to nearest with ties going to nearest even integer (ROUND_HALF_EVEN), instead of being rounding towards minus infinity (ROUND_FLOOR). It’s important that these methods use the same rounding mode than datetime.timedelta to keep the property: (datetime(1970,1,1) + timedelta(seconds=t)) == datetime.utcfromtimestamp(t). It also the rounding mode used by round(float) for example.
- bpo-25155: Fix datetime.datetime.now() and datetime.datetime.utcnow() on Windows to support date after year 2038. It was a regression introduced in Python 3.5.0.
- bpo-25108: Omitted internal frames in traceback functions print_stack(), format_stack(), and extract_stack() called without arguments.
- bpo-25118: Fix a regression of Python 3.5.0 in os.waitpid() on Windows.
- bpo-24684: socket.socket.getaddrinfo() now calls PyUnicode_AsEncodedString() instead of calling the encode() method of the host, to handle correctly custom string with an encode() method which doesn’t return a byte string. The encoder of the IDNA codec is now called directly instead of calling the encode() method of the string.
- bpo-25060: Correctly compute stack usage of the BUILD_MAP opcode.
- bpo-24857: Comparing call_args to a long sequence now correctly returns a boolean result instead of raising an exception. Patch by A Kaptur.
- bpo-23144: Make sure that HTMLParser.feed() returns all the data, even when convert_charrefs is True.
- bpo-24982: shutil.make_archive() with the “zip” format now adds entries for directories (including empty directories) in ZIP file.
- bpo-25019: Fixed a crash caused by setting non-string key of expat parser. Based on patch by John Leitch.
- bpo-16180: Exit pdb if file has syntax error, instead of trapping user in an infinite loop. Patch by Xavier de Gaye.
- bpo-24891: Fix a race condition at Python startup if the file descriptor of stdin (0), stdout (1) or stderr (2) is closed while Python is creating sys.stdin, sys.stdout and sys.stderr objects. These attributes are now set to None if the creation of the object failed, instead of raising an OSError exception. Initial patch written by Marco Paolini.
- bpo-24992: Fix error handling and a race condition (related to garbage collection) in collections.OrderedDict constructor.
- bpo-24881: Fixed setting binary mode in Python implementation of FileIO on Windows and Cygwin. Patch from Akira Li.
- bpo-25578: Fix (another) memory leak in SSLSocket.getpeercer().
- bpo-25530: Disable the vulnerable SSLv3 protocol by default when creating ssl.SSLContext.
- bpo-25569: Fix memory leak in SSLSocket.getpeercert().
- bpo-25471: Sockets returned from accept() shouldn’t appear to be nonblocking.
- bpo-25319: When threading.Event is reinitialized, the underlying condition should use a regular lock rather than a recursive lock.
- bpo-21112: Fix regression in unittest.expectedFailure on subclasses. Patch from Berker Peksag.
- bpo-24764: cgi.FieldStorage.read_multi() now ignores the Content-Length header in part headers. Patch written by Peter Landry and reviewed by Pierre Quentel.
- bpo-24913: Fix overrun error in deque.index(). Found by John Leitch and Bryce Darling.
- bpo-24774: Fix docstring in http.server.test. Patch from Chiu-Hsiang Hsu.
- bpo-21159: Improve message in configparser.InterpolationMissingOptionError. Patch from Łukasz Langa.
- bpo-20362: Honour TestCase.longMessage correctly in assertRegex. Patch from Ilia Kurenkov.
- bpo-23572: Fixed functools.singledispatch on classes with falsy metaclasses. Patch by Ethan Furman.
- asyncio: ensure_future() now accepts awaitable objects.

### IDLE

- bpo-15348: Stop the debugger engine (normally in a user process) before closing the debugger window (running in the IDLE process). This prevents the RuntimeErrors that were being caught and ignored.
- bpo-24455: Prevent IDLE from hanging when a) closing the shell while the debugger is active (15347); b) closing the debugger with the [X] button (15348); and c) activating the debugger when already active (24455). The patch by Mark Roseman does this by making two changes. 1. Suspend and resume the gui.interaction method with the tcl vwait mechanism intended for this purpose (instead of root.mainloop & .quit). 2. In gui.run, allow any existing interaction to terminate first.
- Change ‘The program’ to ‘Your program’ in an IDLE ‘kill program?’ message to make it clearer that the program referred to is the currently running user program, not IDLE itself.
- bpo-24750: Improve the appearance of the IDLE editor window status bar. Patch by Mark Roseman.
- bpo-25313: Change the handling of new built-in text color themes to better address the compatibility problem introduced by the addition of IDLE Dark. Consistently use the revised idleConf.CurrentTheme everywhere in idlelib.
- bpo-24782: Extension configuration is now a tab in the IDLE Preferences dialog rather than a separate dialog. The former tabs are now a sorted list. Patch by Mark Roseman.
- bpo-22726: Re-activate the config dialog help button with some content about the other buttons and the new IDLE Dark theme.
- bpo-24820: IDLE now has an ‘IDLE Dark’ built-in text color theme. It is more or less IDLE Classic inverted, with a cobalt blue background. Strings, comments, keywords, … are still green, red, orange, … . To use it with IDLEs released before November 2015, hit the ‘Save as New Custom Theme’ button and enter a new name, such as ‘Custom Dark’. The custom theme will work with any IDLE release, and can be modified.
- bpo-25224: README.txt is now an idlelib index for IDLE developers and curious users. The previous user content is now in the IDLE doc chapter. ‘IDLE’ now means ‘Integrated Development and Learning Environment’.
- bpo-24820: Users can now set breakpoint colors in Settings -> Custom Highlighting. Original patch by Mark Roseman.
- bpo-24972: Inactive selection background now matches active selection background, as configured by users, on all systems. Found items are now always highlighted on Windows. Initial patch by Mark Roseman.
- bpo-24570: Idle: make calltip and completion boxes appear on Macs affected by a tk regression. Initial patch by Mark Roseman.
- bpo-24988: Idle ScrolledList context menus (used in debugger) now work on Mac Aqua. Patch by Mark Roseman.
- bpo-24801: Make right-click for context menu work on Mac Aqua. Patch by Mark Roseman.
- bpo-25173: Associate tkinter messageboxes with a specific widget. For Mac OSX, make them a ‘sheet’. Patch by Mark Roseman.
- bpo-25198: Enhance the initial html viewer now used for Idle Help. Properly indent fixed-pitch text (patch by Mark Roseman). Give code snippet a very Sphinx-like light blueish-gray background. Re-use initial width and height set by users for shell and editor. When the Table of Contents (TOC) menu is used, put the section header at the top of the screen.
- bpo-25225: Condense and rewrite Idle doc section on text colors.
- bpo-21995: Explain some differences between IDLE and console Python.
- bpo-22820: Explain need for print when running file from Idle editor.
- bpo-25224: Doc: augment Idle feature list and no-subprocess section.
- bpo-25219: Update doc for Idle command line options. Some were missing and notes were not correct.
- bpo-24861: Most of idlelib is private and subject to change. Use idleib.idle.* to start Idle. See idlelib.__init__.__doc__.
- bpo-25199: Idle: add synchronization comments for future maintainers.
- bpo-16893: Replace help.txt with help.html for Idle doc display. The new idlelib/help.html is rstripped Doc/build/html/library/idle.html. It looks better than help.txt and will better document Idle as released. The tkinter html viewer that works for this file was written by Mark Roseman. The now unused EditorWindow.HelpDialog class and helt.txt file are deprecated.
- bpo-24199: Deprecate unused idlelib.idlever with possible removal in 3.6.
- bpo-24790: Remove extraneous code (which also create 2 & 3 conflicts).

### Documentation

- bpo-22558: Add remaining doc links to source code for Python-coded modules. Patch by Yoni Lavi.
- bpo-12067: Rewrite Comparisons section in the Expressions chapter of the language reference. Some of the details of comparing mixed types were incorrect or ambiguous. NotImplemented is only relevant at a lower level than the Expressions chapter. Added details of comparing range() objects, and default behaviour and consistency suggestions for user-defined classes. Patch from Andy Maier.
- bpo-24952: Clarify the default size argument of stack_size() in the “threading” and “_thread” modules. Patch from Mattip.
- bpo-23725: Overhaul tempfile docs. Note deprecated status of mktemp. Patch from Zbigniew Jędrzejewski-Szmek.
- bpo-24808: Update the types of some PyTypeObject fields. Patch by Joseph Weston.
- bpo-22812: Fix unittest discovery examples. Patch from Pam McA’Nulty.

### Tests

- bpo-25449: Added tests for OrderedDict subclasses.
- bpo-25099: Make test_compileall not fail when an entry on sys.path cannot be written to (commonly seen in administrative installs on Windows).
- bpo-23919: Prevents assert dialogs appearing in the test suite.
- `PCbuild\rt.bat` now accepts an unlimited number of arguments to pass along to regrtest.py. Previously there was a limit of 9.

### Build

- bpo-24915: Add LLVM support for PGO builds and use the test suite to generate the profile data. Initial patch by Alecsandru Patrascu of Intel.
- bpo-24910: Windows MSIs now have unique display names.
- bpo-24986: It is now possible to build Python on Windows without errors when external libraries are not available.

### Windows

- bpo-25450: Updates shortcuts to start Python in installation directory.
- bpo-25164: Changes default all-users install directory to match per-user directory.
- bpo-25143: Improves installer error messages for unsupported platforms.
- bpo-25163: Display correct directory in installer when using non-default settings.
- bpo-25361: Disables use of SSE2 instructions in Windows 32-bit build
- bpo-25089: Adds logging to installer for case where launcher is not selected on upgrade.
- bpo-25165: Windows uninstallation should not remove launcher if other versions remain
- bpo-25112: py.exe launcher is missing icons
- bpo-25102: Windows installer does not precompile for -O or -OO.
- bpo-25081: Makes Back button in installer go back to upgrade page when upgrading.
- bpo-25091: Increases font size of the installer.
- bpo-25126: Clarifies that the non-web installer will download some components.
- bpo-25213: Restores requestedExecutionLevel to manifest to disable UAC virtualization.
- bpo-25022: Removed very outdated PC/example_nt/ directory.

### Tools/Demos

- bpo-25440: Fix output of python-config –extension-suffix.

## Python 3.5.0 final

Release date: 2015-09-13

### Build

- bpo-25071: Windows installer should not require TargetDir parameter when installing quietly.

## Python 3.5.0 release candidate 4

Release date: 2015-09-09

### Library

- bpo-25029: Fixes MemoryError in test_strptime.

### Build

- bpo-25027: Reverts partial-static build options and adds vcruntime140.dll to Windows installation.

## Python 3.5.0 release candidate 3

Release date: 2015-09-07

### Core and Builtins

- bpo-24305: Prevent import subsystem stack frames from being counted by the warnings.warn(stacklevel=) parameter.
- bpo-24912: Prevent __class__ assignment to immutable built-in objects.
- bpo-24975: Fix AST compilation for PEP 448 syntax.

### Library

- bpo-24917: time_strftime() buffer over-read.
- bpo-24748: To resolve a compatibility problem found with py2exe and pywin32, imp.load_dynamic() once again ignores previously loaded modules to support Python modules replacing themselves with extension modules. Patch by Petr Viktorin.
- bpo-24635: Fixed a bug in typing.py where isinstance([], typing.Iterable) would return True once, then False on subsequent calls.
- bpo-24989: Fixed buffer overread in BytesIO.readline() if a position is set beyond size. Based on patch by John Leitch.
- bpo-24913: Fix overrun error in deque.index(). Found by John Leitch and Bryce Darling.

## Python 3.5.0 release candidate 2

Release date: 2015-08-25

### Core and Builtins

- bpo-24769: Interpreter now starts properly when dynamic loading is disabled. Patch by Petr Viktorin.
- bpo-21167: NAN operations are now handled correctly when python is compiled with ICC even if -fp-model strict is not specified.
- bpo-24492: A “package” lacking a __name__ attribute when trying to perform a `from .. import ...` statement will trigger an ImportError instead of an AttributeError.

### Library

- bpo-24847: Removes vcruntime140.dll dependency from Tcl/Tk.
- bpo-24839: platform._syscmd_ver raises DeprecationWarning
- bpo-24867: Fix Task.get_stack() for ‘async def’ coroutines

## Python 3.5.0 release candidate 1

Release date: 2015-08-09

### Core and Builtins

- bpo-24667: Resize odict in all cases that the underlying dict resizes.

### Library

- bpo-24824: Signatures of codecs.encode() and codecs.decode() now are compatible with pydoc.
- bpo-24634: Importing uuid should not try to load libc on Windows
- bpo-24798: _msvccompiler.py doesn’t properly support manifests
- bpo-4395: Better testing and documentation of binary operators. Patch by Martin Panter.
- bpo-23973: Update typing.py from GitHub repo.
- bpo-23004: mock_open() now reads binary data correctly when the type of read_data is bytes. Initial patch by Aaron Hill.
- bpo-23888: Handle fractional time in cookie expiry. Patch by ssh.
- bpo-23652: Make it possible to compile the select module against the libc headers from the Linux Standard Base, which do not include some EPOLL macros. Patch by Matt Frank.
- bpo-22932: Fix timezones in email.utils.formatdate. Patch from Dmitry Shachnev.
- bpo-23779: imaplib raises TypeError if authenticator tries to abort. Patch from Craig Holmquist.
- bpo-23319: Fix ctypes.BigEndianStructure, swap correctly bytes. Patch written by Matthieu Gautier.
- bpo-23254: Document how to close the TCPServer listening socket. Patch from Martin Panter.
- bpo-19450: Update Windows and OS X installer builds to use SQLite 3.8.11.
- bpo-17527: Add PATCH to wsgiref.validator. Patch from Luca Sbardella.
- bpo-24791: Fix grammar regression for call syntax: ‘g(*a or b)’.

### IDLE

- bpo-23672: Allow Idle to edit and run files with astral chars in name. Patch by Mohd Sanad Zaki Rizvi.
- bpo-24745: Idle editor default font. Switch from Courier to platform-sensitive TkFixedFont. This should not affect current customized font selections. If there is a problem, edit $HOME/.idlerc/config-main.cfg and remove ‘fontxxx’ entries from [Editor Window]. Patch by Mark Roseman.
- bpo-21192: Idle editor. When a file is run, put its name in the restart bar. Do not print false prompts. Original patch by Adnan Umer.
- bpo-13884: Idle menus. Remove tearoff lines. Patch by Roger Serwy.

### Documentation

- bpo-24129: Clarify the reference documentation for name resolution. This includes removing the assumption that readers will be familiar with the name resolution scheme Python used prior to the introduction of lexical scoping for function namespaces. Patch by Ivan Levkivskyi.
- bpo-20769: Improve reload() docs. Patch by Dorian Pula.
- bpo-23589: Remove duplicate sentence from the FAQ. Patch by Yongzhi Pan.
- bpo-24729: Correct IO tutorial to match implementation regarding encoding parameter to open function.

### Tests

- bpo-24751: When running regrtest with the `-w` command line option, a test run is no longer marked as a failure if all tests succeed when re-run.

## Python 3.5.0 beta 4

Release date: 2015-07-26

### Core and Builtins

- bpo-23573: Restored optimization of bytes.rfind() and bytearray.rfind() for single-byte argument on Linux.
- bpo-24569: Make PEP 448 dictionary evaluation more consistent.
- bpo-24583: Fix crash when set is mutated while being updated.
- bpo-24407: Fix crash when dict is mutated while being updated.
- bpo-24619: New approach for tokenizing async/await. As a consequence, it is now possible to have one-line ‘async def foo(): await ..’ functions.
- bpo-24687: Plug refleak on SyntaxError in function parameters annotations.
- bpo-15944: memoryview: Allow arbitrary formats when casting to bytes. Patch by Martin Panter.

### Library

- bpo-23441: rcompleter now prints a tab character instead of displaying possible completions for an empty word. Initial patch by Martin Sekera.
- bpo-24683: Fixed crashes in _json functions called with arguments of inappropriate type.
- bpo-21697: shutil.copytree() now correctly handles symbolic links that point to directories. Patch by Eduardo Seabra and Thomas Kluyver.
- bpo-14373: Fixed segmentation fault when gc.collect() is called during constructing lru_cache (C implementation).
- bpo-24695: Fix a regression in traceback.print_exception(). If exc_traceback is None we shouldn’t print a traceback header like described in the documentation.
- bpo-24620: Random.setstate() now validates the value of state last element.
- bpo-22485: Fixed an issue that caused `inspect.getsource` to return incorrect results on nested functions.
- bpo-22153: Improve unittest docs. Patch from Martin Panter and evilzero.
- bpo-24580: Symbolic group references to open group in re patterns now are explicitly forbidden as well as numeric group references.
- bpo-24206: Fixed __eq__ and __ne__ methods of inspect classes.
- bpo-24631: Fixed regression in the timeit module with multiline setup.
- bpo-18622: unittest.mock.mock_open().reset_mock would recurse infinitely. Patch from Nicola Palumbo and Laurent De Buyst.
- bpo-23661: unittest.mock side_effects can now be exceptions again. This was a regression vs Python 3.4. Patch from Ignacio Rossi
- bpo-24608: chunk.Chunk.read() now always returns bytes, not str.
- bpo-18684: Fixed reading out of the buffer in the re module.
- bpo-24259: tarfile now raises a ReadError if an archive is truncated inside a data segment.
- bpo-15014: SMTP.auth() and SMTP.login() now support RFC 4954’s optional initial-response argument to the SMTP AUTH command.
- bpo-24669: Fix inspect.getsource() for ‘async def’ functions. Patch by Kai Groner.
- bpo-24688: ast.get_docstring() for ‘async def’ functions.

### Build

- bpo-24603: Update Windows builds and OS X 10.5 installer to use OpenSSL 1.0.2d.

## Python 3.5.0 beta 3

Release date: 2015-07-05

### Core and Builtins

- bpo-24467: Fixed possible buffer over-read in bytearray. The bytearray object now always allocates place for trailing null byte and it’s buffer now is always null-terminated.
- Upgrade to Unicode 8.0.0.
- bpo-24345: Add Py_tp_finalize slot for the stable ABI.
- bpo-24400: Introduce a distinct type for PEP 492 coroutines; add types.CoroutineType, inspect.getcoroutinestate, inspect.getcoroutinelocals; coroutines no longer use CO_GENERATOR flag; sys.set_coroutine_wrapper works only for ‘async def’ coroutines; inspect.iscoroutine no longer uses collections.abc.Coroutine, it’s intended to test for pure ‘async def’ coroutines only; add new opcode: GET_YIELD_FROM_ITER; fix generators wrapper used in types.coroutine to be instance of collections.abc.Generator; collections.abc.Awaitable and collections.abc.Coroutine can no longer be used to detect generator-based coroutines–use inspect.isawaitable instead.
- bpo-24450: Add gi_yieldfrom to generators and cr_await to coroutines. Contributed by Benno Leslie and Yury Selivanov.
- bpo-19235: Add new RecursionError exception. Patch by Georg Brandl.

### Library

- bpo-21750: mock_open.read_data can now be read from each instance, as it could in Python 3.3.
- bpo-24552: Fix use after free in an error case of the _pickle module.
- bpo-24514: tarfile now tolerates number fields consisting of only whitespace.
- bpo-19176: Fixed doctype() related bugs in C implementation of ElementTree. A deprecation warning no longer issued by XMLParser subclass with default doctype() method. Direct call of doctype() now issues a warning. Parser’s doctype() now is not called if target’s doctype() is called. Based on patch by Martin Panter.
- bpo-20387: Restore semantic round-trip correctness in tokenize/untokenize for tab-indented blocks.
- bpo-24456: Fixed possible buffer over-read in adpcm2lin() and lin2adpcm() functions of the audioop module.
- bpo-24336: The contextmanager decorator now works with functions with keyword arguments called “func” and “self”. Patch by Martin Panter.
- bpo-24522: Fix possible integer overflow in json accelerator module.
- bpo-24489: ensure a previously set C errno doesn’t disturb cmath.polar().
- bpo-24408: Fixed AttributeError in measure() and metrics() methods of tkinter.Font.
- bpo-14373: C implementation of functools.lru_cache() now can be used with methods.
- bpo-24347: Set KeyError if PyDict_GetItemWithError returns NULL.
- bpo-24348: Drop superfluous incref/decref.
- bpo-24359: Check for changed OrderedDict size during iteration.
- bpo-24368: Support keyword arguments in OrderedDict methods.
- bpo-24362: Simplify the C OrderedDict fast nodes resize logic.
- bpo-24377: Fix a ref leak in OrderedDict.__repr__.
- bpo-24369: Defend against key-changes during iteration.

### Tests

- bpo-24373: _testmultiphase and xxlimited now use tp_traverse and tp_finalize to avoid reference leaks encountered when combining tp_dealloc with PyType_FromSpec (see bpo-16690 for details)

### Documentation

- bpo-24458: Update documentation to cover multi-phase initialization for extension modules (PEP 489). Patch by Petr Viktorin.
- bpo-24351: Clarify what is meant by “identifier” in the context of string.Template instances.

### Build

- bpo-24432: Update Windows builds and OS X 10.5 installer to use OpenSSL 1.0.2c.

## Python 3.5.0 beta 2

Release date: 2015-05-31

### Core and Builtins

- bpo-24284: The startswith and endswith methods of the str class no longer return True when finding the empty string and the indexes are completely out of range.
- bpo-24115: Update uses of PyObject_IsTrue(), PyObject_Not(), PyObject_IsInstance(), PyObject_RichCompareBool() and _PyDict_Contains() to check for and handle errors correctly.
- bpo-24328: Fix importing one character extension modules.
- bpo-11205: In dictionary displays, evaluate the key before the value.
- bpo-24285: Fixed regression that prevented importing extension modules from inside packages. Patch by Petr Viktorin.

### Library

- bpo-23247: Fix a crash in the StreamWriter.reset() of CJK codecs.
- bpo-24270: Add math.isclose() and cmath.isclose() functions as per PEP 485. Contributed by Chris Barker and Tal Einat.
- bpo-5633: Fixed timeit when the statement is a string and the setup is not.
- bpo-24326: Fixed audioop.ratecv() with non-default weightB argument. Original patch by David Moore.
- bpo-16991: Add a C implementation of OrderedDict.
- bpo-23934: Fix inspect.signature to fail correctly for builtin types lacking signature information. Initial patch by James Powell.

## Python 3.5.0 beta 1

Release date: 2015-05-24

### Core and Builtins

- bpo-24276: Fixed optimization of property descriptor getter.
- bpo-24268: PEP 489: Multi-phase extension module initialization. Patch by Petr Viktorin.
- bpo-23955: Add pyvenv.cfg option to suppress registry/environment lookup for generating sys.path on Windows.
- bpo-24257: Fixed system error in the comparison of faked types.SimpleNamespace.
- bpo-22939: Fixed integer overflow in iterator object. Patch by Clement Rouault.
- bpo-23985: Fix a possible buffer overrun when deleting a slice from the front of a bytearray and then appending some other bytes data.
- bpo-24102: Fixed exception type checking in standard error handlers.
- bpo-15027: The UTF-32 encoder is now 3x to 7x faster.
- bpo-23290: Optimize set_merge() for cases where the target is empty. (Contributed by Serhiy Storchaka.)
- bpo-2292: PEP 448: Additional Unpacking Generalizations.
- bpo-24096: Make warnings.warn_explicit more robust against mutation of the warnings.filters list.
- bpo-23996: Avoid a crash when a delegated generator raises an unnormalized StopIteration exception. Patch by Stefan Behnel.
- bpo-23910: Optimize property() getter calls. Patch by Joe Jevnik.
- bpo-23911: Move path-based importlib bootstrap code to a separate frozen module.
- bpo-24192: Fix namespace package imports.
- bpo-24022: Fix tokenizer crash when processing undecodable source code.
- bpo-9951: Added a hex() method to bytes, bytearray, and memoryview.
- bpo-22906: PEP 479: Change StopIteration handling inside generators.
- bpo-24017: PEP 492: Coroutines with async and await syntax.

### Library

- bpo-14373: Added C implementation of functools.lru_cache(). Based on patches by Matt Joiner and Alexey Kachayev.
- bpo-24230: The tempfile module now accepts bytes for prefix, suffix and dir parameters and returns bytes in such situations (matching the os module APIs).
- bpo-22189: collections.UserString now supports __getnewargs__(), __rmod__(), casefold(), format_map(), isprintable(), and maketrans(). Patch by Joe Jevnik.
- bpo-24244: Prevents termination when an invalid format string is encountered on Windows in strftime.
- bpo-23973: PEP 484: Add the typing module.
- bpo-23086: The collections.abc.Sequence() abstract base class added start and stop parameters to the index() mixin. Patch by Devin Jeanpierre.
- bpo-20035: Replaced the `tkinter._fix` module used for setting up the Tcl/Tk environment on Windows with a private function in the `_tkinter` module that makes no permanent changes to the environment.
- bpo-24257: Fixed segmentation fault in sqlite3.Row constructor with faked cursor type.
- bpo-15836: assertRaises(), assertRaisesRegex(), assertWarns() and assertWarnsRegex() assertments now check the type of the first argument to prevent possible user error. Based on patch by Daniel Wagner-Hall.
- bpo-9858: Add missing method stubs to _io.RawIOBase. Patch by Laura Rupprecht.
- bpo-22955: attrgetter, itemgetter and methodcaller objects in the operator module now support pickling. Added readable and evaluable repr for these objects. Based on patch by Josh Rosenberg.
- bpo-22107: tempfile.gettempdir() and tempfile.mkdtemp() now try again when a directory with the chosen name already exists on Windows as well as on Unix. tempfile.mkstemp() now fails early if parent directory is not valid (not exists or is a file) on Windows.
- bpo-23780: Improved error message in os.path.join() with single argument.
- bpo-6598: Increased time precision and random number range in email.utils.make_msgid() to strengthen the uniqueness of the message ID.
- bpo-24091: Fixed various crashes in corner cases in C implementation of ElementTree.
- bpo-21931: msilib.FCICreate() now raises TypeError in the case of a bad argument instead of a ValueError with a bogus FCI error number. Patch by Jeffrey Armstrong.
- bpo-13866: quote_via argument added to urllib.parse.urlencode.
- bpo-20098: New mangle_from policy option for email, default True for compat32, but False for all other policies.
- bpo-24211: The email library now supports RFC 6532: it can generate headers using utf-8 instead of encoded words.
- bpo-16314: Added support for the LZMA compression in distutils.
- bpo-21804: poplib now supports RFC 6856 (UTF8).
- bpo-18682: Optimized pprint functions for builtin scalar types.
- bpo-22027: smtplib now supports RFC 6531 (SMTPUTF8).
- bpo-23488: Random generator objects now consume 2x less memory on 64-bit.
- bpo-1322: platform.dist() and platform.linux_distribution() functions are now deprecated. Initial patch by Vajrasky Kok.
- bpo-22486: Added the math.gcd() function. The fractions.gcd() function now is deprecated. Based on patch by Mark Dickinson.
- bpo-24064: Property() docstrings are now writeable. (Patch by Berker Peksag.)
- bpo-22681: Added support for the koi8_t encoding.
- bpo-22682: Added support for the kz1048 encoding.
- bpo-23796: peek and read1 methods of BufferedReader now raise ValueError if they called on a closed object. Patch by John Hergenroeder.
- bpo-21795: smtpd now supports the 8BITMIME extension whenever the new decode_data constructor argument is set to False.
- bpo-24155: optimize heapq.heapify() for better cache performance when heapifying large lists.
- bpo-21800: imaplib now supports RFC 5161 (enable), RFC 6855 (utf8/internationalized email) and automatically encodes non-ASCII usernames and passwords to UTF8.
- bpo-20274: When calling a _sqlite.Connection, it now complains if passed any keyword arguments. Previously it silently ignored them.
- bpo-20274: Remove ignored and erroneous “kwargs” parameters from three METH_VARARGS methods on _sqlite.Connection.
- bpo-24134: assertRaises(), assertRaisesRegex(), assertWarns() and assertWarnsRegex() checks now emits a deprecation warning when callable is None or keyword arguments except msg is passed in the context manager mode.
- bpo-24018: Add a collections.abc.Generator abstract base class. Contributed by Stefan Behnel.
- bpo-23880: Tkinter’s getint() and getdouble() now support Tcl_Obj. Tkinter’s getdouble() now supports any numbers (in particular int).
- bpo-22619: Added negative limit support in the traceback module. Based on patch by Dmitry Kazakov.
- bpo-24094: Fix possible crash in json.encode with poorly behaved dict subclasses.
- bpo-9246: On POSIX, os.getcwd() now supports paths longer than 1025 bytes. Patch written by William Orr.
- bpo-17445: add difflib.diff_bytes() to support comparison of byte strings (fixes a regression from Python 2).
- bpo-23917: Fall back to sequential compilation when ProcessPoolExecutor doesn’t exist. Patch by Claudiu Popa.
- bpo-23008: Fixed resolving attributes with boolean value is False in pydoc.
- Fix asyncio issue 235: LifoQueue and PriorityQueue’s put didn’t increment unfinished tasks (this bug was introduced when JoinableQueue was merged with Queue).
- bpo-23908: os functions now reject paths with embedded null character on Windows instead of silently truncating them.
- bpo-23728: binascii.crc_hqx() could return an integer outside of the range 0-0xffff for empty data.
- bpo-23887: urllib.error.HTTPError now has a proper repr() representation. Patch by Berker Peksag.
- asyncio: New event loop APIs: set_task_factory() and get_task_factory().
- asyncio: async() function is deprecated in favour of ensure_future().
- bpo-24178: asyncio.Lock, Condition, Semaphore, and BoundedSemaphore support new ‘async with’ syntax. Contributed by Yury Selivanov.
- bpo-24179: Support ‘async for’ for asyncio.StreamReader. Contributed by Yury Selivanov.
- bpo-24184: Add AsyncIterator and AsyncIterable ABCs to collections.abc. Contributed by Yury Selivanov.
- bpo-22547: Implement informative __repr__ for inspect.BoundArguments. Contributed by Yury Selivanov.
- bpo-24190: Implement inspect.BoundArgument.apply_defaults() method. Contributed by Yury Selivanov.
- bpo-20691: Add ‘follow_wrapped’ argument to inspect.Signature.from_callable() and inspect.signature(). Contributed by Yury Selivanov.
- bpo-24248: Deprecate inspect.Signature.from_function() and inspect.Signature.from_builtin().
- bpo-23898: Fix inspect.classify_class_attrs() to support attributes with overloaded __eq__ and __bool__. Patch by Mike Bayer.
- bpo-24298: Fix inspect.signature() to correctly unwrap wrappers around bound methods.

### IDLE

- bpo-23184: remove unused names and imports in idlelib. Initial patch by Al Sweigart.

### Tests

- bpo-21520: test_zipfile no longer fails if the word ‘bad’ appears anywhere in the name of the current directory.
- bpo-9517: Move script_helper into the support package. Patch by Christie Wilson.

### Documentation

- bpo-22155: Add File Handlers subsection with createfilehandler to tkinter doc. Remove obsolete example from FAQ. Patch by Martin Panter.
- bpo-24029: Document the name binding behavior for submodule imports.
- bpo-24077: Fix typo in man page for -I command option: -s, not -S

### Tools/Demos

- bpo-24000: Improved Argument Clinic’s mapping of converters to legacy “format units”. Updated the documentation to match.
- bpo-24001: Argument Clinic converters now use accept={type} instead of types={‘type’} to specify the types the converter accepts.
- bpo-23330: h2py now supports arbitrary filenames in #include.
- bpo-24031: make patchcheck now supports git checkouts, too.

## Python 3.5.0 alpha 4

Release date: 2015-04-19

### Core and Builtins

- bpo-22980: Under Linux, GNU/KFreeBSD and the Hurd, C extensions now include the architecture triplet in the extension name, to make it easy to test builds for different ABIs in the same working tree. Under OS X, the extension name now includes PEP 3149-style information.
- bpo-22631: Added Linux-specific socket constant CAN_RAW_FD_FRAMES. Patch courtesy of Joe Jevnik.
- bpo-23731: Implement PEP 488: removal of .pyo files.
- bpo-23726: Don’t enable GC for user subclasses of non-GC types that don’t add any new fields. Patch by Eugene Toder.
- bpo-23309: Avoid a deadlock at shutdown if a daemon thread is aborted while it is holding a lock to a buffered I/O object, and the main thread tries to use the same I/O object (typically stdout or stderr). A fatal error is emitted instead.
- bpo-22977: Fixed formatting Windows error messages on Wine. Patch by Martin Panter.
- bpo-23466: %c, %o, %x, and %X in bytes formatting now raise TypeError on non-integer input.
- bpo-24044: Fix possible null pointer dereference in list.sort in out of memory conditions.
- bpo-21354: PyCFunction_New function is exposed by python DLL again.

### Library

- bpo-23840: tokenize.open() now closes the temporary binary file on error to fix a resource warning.
- bpo-16914: new debuglevel 2 in smtplib adds timestamps to debug output.
- bpo-7159: urllib.request now supports sending auth credentials automatically after the first 401. This enhancement is a superset of the enhancement from bpo-19494 and supersedes that change.
- bpo-23703: Fix a regression in urljoin() introduced in 901e4e52b20a. Patch by Demian Brecht.
- bpo-4254: Adds _curses.update_lines_cols(). Patch by Arnon Yaari
- bpo-19933: Provide default argument for ndigits in round. Patch by Vajrasky Kok.
- bpo-23193: Add a numeric_owner parameter to tarfile.TarFile.extract and tarfile.TarFile.extractall. Patch by Michael Vogt and Eric Smith.
- bpo-23342: Add a subprocess.run() function than returns a CalledProcess instance for a more consistent API than the existing call* functions.
- bpo-21217: inspect.getsourcelines() now tries to compute the start and end lines from the code object, fixing an issue when a lambda function is used as decorator argument. Patch by Thomas Ballinger and Allison Kaptur.
- bpo-24521: Fix possible integer overflows in the pickle module.
- bpo-22931: Allow ‘[‘ and ‘]’ in cookie values.
- The keywords attribute of functools.partial is now always a dictionary.
- bpo-23811: Add missing newline to the PyCompileError error message. Patch by Alex Shkop.
- bpo-21116: Avoid blowing memory when allocating a multiprocessing shared array that’s larger than 50% of the available RAM. Patch by Médéric Boquien.
- bpo-22982: Improve BOM handling when seeking to multiple positions of a writable text file.
- bpo-23464: Removed deprecated asyncio JoinableQueue.
- bpo-23529: Limit the size of decompressed data when reading from GzipFile, BZ2File or LZMAFile. This defeats denial of service attacks using compressed bombs (i.e. compressed payloads which decompress to a huge size). Patch by Martin Panter and Nikolaus Rath.
- bpo-21859: Added Python implementation of io.FileIO.
- bpo-23865: close() methods in multiple modules now are idempotent and more robust at shutdown. If they need to release multiple resources, all are released even if errors occur.
- bpo-23400: Raise same exception on both Python 2 and 3 if sem_open is not available. Patch by Davin Potts.
- bpo-10838: The subprocess now module includes SubprocessError and TimeoutError in its list of exported names for the users wild enough to use `from subprocess import *`.
- bpo-23411: Added DefragResult, ParseResult, SplitResult, DefragResultBytes, ParseResultBytes, and SplitResultBytes to urllib.parse.__all__. Patch by Martin Panter.
- bpo-23881: urllib.request.ftpwrapper constructor now closes the socket if the FTP connection failed to fix a ResourceWarning.
- bpo-23853: `socket.socket.sendall()` does no more reset the socket timeout each time data is sent successfully. The socket timeout is now the maximum total duration to send all data.
- bpo-22721: An order of multiline pprint output of set or dict containing orderable and non-orderable elements no longer depends on iteration order of set or dict.
- bpo-15133: _tkinter.tkapp.getboolean() now supports Tcl_Obj and always returns bool. tkinter.BooleanVar now validates input values (accepted bool, int, str, and Tcl_Obj). tkinter.BooleanVar.get() now always returns bool.
- bpo-10590: xml.sax.parseString() now supports string argument.
- bpo-23338: Fixed formatting ctypes error messages on Cygwin. Patch by Makoto Kato.
- bpo-15582: inspect.getdoc() now follows inheritance chains.
- bpo-2175: SAX parsers now support a character stream of InputSource object.
- bpo-16840: Tkinter now supports 64-bit integers added in Tcl 8.4 and arbitrary precision integers added in Tcl 8.5.
- bpo-23834: Fix socket.sendto(), use the C Py_ssize_t type to store the result of sendto() instead of the C int type.
- bpo-23618: `socket.socket.connect()` now waits until the connection completes instead of raising `InterruptedError` if the connection is interrupted by signals, signal handlers don’t raise an exception and the socket is blocking or has a timeout. `socket.socket.connect()` still raise `InterruptedError` for non-blocking sockets.
- bpo-21526: Tkinter now supports new boolean type in Tcl 8.5.
- bpo-23836: Fix the faulthandler module to handle reentrant calls to its signal handlers.
- bpo-23838: linecache now clears the cache and returns an empty result on MemoryError.
- bpo-10395: Added os.path.commonpath(). Implemented in posixpath and ntpath. Based on patch by Rafik Draoui.
- bpo-23611: Serializing more “lookupable” objects (such as unbound methods or nested classes) now are supported with pickle protocols < 4.
- bpo-13583: sqlite3.Row now supports slice indexing.
- bpo-18473: Fixed 2to3 and 3to2 compatible pickle mappings. Fixed ambiguous reverse mappings. Added many new mappings. Import mapping is no longer applied to modules already mapped with full name mapping.
- bpo-23485: select.select() is now retried automatically with the recomputed timeout when interrupted by a signal, except if the signal handler raises an exception. This change is part of the PEP 475.
- bpo-23752: When built from an existing file descriptor, io.FileIO() now only calls fstat() once. Before fstat() was called twice, which was not necessary.
- bpo-23704: collections.deque() objects now support __add__, __mul__, and __imul__().
- bpo-23171: csv.Writer.writerow() now supports arbitrary iterables.
- bpo-23745: The new email header parser now handles duplicate MIME parameter names without error, similar to how get_param behaves.
- bpo-22117: Fix os.utime(), it now rounds the timestamp towards minus infinity (-inf) instead of rounding towards zero.
- bpo-23310: Fix MagicMock’s initializer to work with __methods__, just like configure_mock(). Patch by Kasia Jachim.

### Build

- bpo-23817: FreeBSD now uses “1.0” in the SOVERSION as other operating systems, instead of just “1”.
- bpo-23501: Argument Clinic now generates code into separate files by default.

### Tests

- bpo-23799: Added test.support.start_threads() for running and cleaning up multiple threads.
- bpo-22390: test.regrtest now emits a warning if temporary files or directories are left after running a test.

### Tools/Demos

- bpo-18128: pygettext now uses standard +NNNN format in the POT-Creation-Date header.
- bpo-23935: Argument Clinic’s understanding of format units accepting bytes, bytearrays, and buffers is now consistent with both the documentation and the implementation.
- bpo-23944: Argument Clinic now wraps long impl prototypes at column 78.
- bpo-20586: Argument Clinic now ensures that functions without docstrings have signatures.
- bpo-23492: Argument Clinic now generates argument parsing code with PyArg_Parse instead of PyArg_ParseTuple if possible.
- bpo-23500: Argument Clinic is now smarter about generating the “#ifndef” (empty) definition of the methoddef macro: it’s only generated once, even if Argument Clinic processes the same symbol multiple times, and it’s emitted at the end of all processing rather than immediately after the first use.

### C API

- bpo-23998: PyImport_ReInitLock() now checks for lock allocation error

## Python 3.5.0 alpha 3

Release date: 2015-03-28

### Core and Builtins

- bpo-23573: Increased performance of string search operations (str.find, str.index, str.count, the in operator, str.split, str.partition) with arguments of different kinds (UCS1, UCS2, UCS4).
- bpo-23753: Python doesn’t support anymore platforms without stat() or fstat(), these functions are always required.
- bpo-23681: The -b option now affects comparisons of bytes with int.
- bpo-23632: Memoryviews now allow tuple indexing (including for multi-dimensional memoryviews).
- bpo-23192: Fixed generator lambdas. Patch by Bruno Cauet.
- bpo-23629: Fix the default __sizeof__ implementation for variable-sized objects.

### Library

- bpo-14260: The groupindex attribute of regular expression pattern object now is non-modifiable mapping.
- bpo-23792: Ignore KeyboardInterrupt when the pydoc pager is active. This mimics the behavior of the standard unix pagers, and prevents pipepager from shutting down while the pager itself is still running.
- bpo-23775: pprint() of OrderedDict now outputs the same representation as repr().
- bpo-23765: Removed IsBadStringPtr calls in ctypes
- bpo-22364: Improved some re error messages using regex for hints.
- bpo-23742: ntpath.expandvars() no longer loses unbalanced single quotes.
- bpo-21717: The zipfile.ZipFile.open function now supports ‘x’ (exclusive creation) mode.
- bpo-21802: The reader in BufferedRWPair now is closed even when closing writer failed in BufferedRWPair.close().
- bpo-23622: Unknown escapes in regular expressions that consist of `'\'` and ASCII letter now raise a deprecation warning and will be forbidden in Python 3.6.
- bpo-23671: string.Template now allows specifying the “self” parameter as a keyword argument. string.Formatter now allows specifying the “self” and the “format_string” parameters as keyword arguments.
- bpo-23502: The pprint module now supports mapping proxies.
- bpo-17530: pprint now wraps long bytes objects and bytearrays.
- bpo-22687: Fixed some corner cases in breaking words in tetxtwrap. Got rid of quadratic complexity in breaking long words.
- bpo-4727: The copy module now uses pickle protocol 4 (PEP 3154) and supports copying of instances of classes whose __new__ method takes keyword-only arguments.
- bpo-23491: Added a zipapp module to support creating executable zip file archives of Python code. Registered “.pyz” and “.pyzw” extensions on Windows for these archives (PEP 441).
- bpo-23657: Avoid explicit checks for str in zipapp, adding support for pathlib.Path objects as arguments.
- bpo-23688: Added support of arbitrary bytes-like objects and avoided unnecessary copying of memoryview in gzip.GzipFile.write(). Original patch by Wolfgang Maier.
- bpo-23252: Added support for writing ZIP files to unseekable streams.
- bpo-23647: Increase imaplib’s MAXLINE to accommodate modern mailbox sizes.
- bpo-23539: If body is None, http.client.HTTPConnection.request now sets Content-Length to 0 for PUT, POST, and PATCH headers to avoid 411 errors from some web servers.
- bpo-22351: The nntplib.NNTP constructor no longer leaves the connection and socket open until the garbage collector cleans them up. Patch by Martin Panter.
- bpo-23704: collections.deque() objects now support methods for index(), insert(), and copy(). This allows deques to be registered as a MutableSequence and it improves their substitutability for lists.
- bpo-23715: `signal.sigwaitinfo()` and `signal.sigtimedwait()` are now retried when interrupted by a signal not in the sigset parameter, if the signal handler does not raise an exception. signal.sigtimedwait() recomputes the timeout with a monotonic clock when it is retried.
- bpo-23001: Few functions in modules mmap, ossaudiodev, socket, ssl, and codecs, that accepted only read-only bytes-like object now accept writable bytes-like object too.
- bpo-23646: If time.sleep() is interrupted by a signal, the sleep is now retried with the recomputed delay, except if the signal handler raises an exception (PEP 475).
- bpo-23136: _strptime now uniformly handles all days in week 0, including Dec 30 of previous year. Based on patch by Jim Carroll.
- bpo-23700: Iterator of NamedTemporaryFile now keeps a reference to NamedTemporaryFile instance. Patch by Bohuslav Kabrda.
- bpo-22903: The fake test case created by unittest.loader when it fails importing a test module is now picklable.
- bpo-22181: On Linux, os.urandom() now uses the new getrandom() syscall if available, syscall introduced in the Linux kernel 3.17. It is more reliable and more secure, because it avoids the need of a file descriptor and waits until the kernel has enough entropy.
- bpo-2211: Updated the implementation of the http.cookies.Morsel class. Setting attributes key, value and coded_value directly now is deprecated. update() and setdefault() now transform and check keys. Comparing for equality now takes into account attributes key, value and coded_value. copy() now returns a Morsel, not a dict. repr() now contains all attributes. Optimized checking keys and quoting values. Added new tests. Original patch by Demian Brecht.
- bpo-18983: Allow selection of output units in timeit. Patch by Julian Gindi.
- bpo-23631: Fix traceback.format_list when a traceback has been mutated.
- bpo-23568: Add rdivmod support to MagicMock() objects. Patch by Håkan Lövdahl.
- bpo-2052: Add charset parameter to HtmlDiff.make_file().
- bpo-23668: Support os.truncate and os.ftruncate on Windows.
- bpo-23138: Fixed parsing cookies with absent keys or values in cookiejar. Patch by Demian Brecht.
- bpo-23051: multiprocessing.Pool methods imap() and imap_unordered() now handle exceptions raised by an iterator. Patch by Alon Diamant and Davin Potts.
- bpo-23581: Add matmul support to MagicMock. Patch by Håkan Lövdahl.
- bpo-23566: enable(), register(), dump_traceback() and dump_traceback_later() functions of faulthandler now accept file descriptors. Patch by Wei Wu.
- bpo-22928: Disabled HTTP header injections in http.client. Original patch by Demian Brecht.
- bpo-23615: Modules bz2, tarfile and tokenize now can be reloaded with imp.reload(). Patch by Thomas Kluyver.
- bpo-23605: os.walk() now calls os.scandir() instead of os.listdir(). The usage of os.scandir() reduces the number of calls to os.stat(). Initial patch written by Ben Hoyt.

### Build

- bpo-23585: make patchcheck will ensure the interpreter is built.

### Tests

- bpo-23583: Added tests for standard IO streams in IDLE.
- bpo-22289: Prevent test_urllib2net failures due to ftp connection timeout.

### Tools/Demos

- bpo-22826: The result of open() in Tools/freeze/bkfile.py is now better compatible with regular files (in particular it now supports the context management protocol).

## Python 3.5.0 alpha 2

Release date: 2015-03-09

### Core and Builtins

- bpo-23571: PyObject_Call() and PyCFunction_Call() now raise a SystemError if a function returns a result and raises an exception. The SystemError is chained to the previous exception.

### Library

- bpo-22524: New os.scandir() function, part of the PEP 471: “os.scandir() function – a better and faster directory iterator”. Patch written by Ben Hoyt.

- bpo-23103: Reduced the memory consumption of IPv4Address and IPv6Address.

- bpo-21793: BaseHTTPRequestHandler again logs response code as numeric, not as stringified enum. Patch by Demian Brecht.

- bpo-23476: In the ssl module, enable OpenSSL’s X509_V_FLAG_TRUSTED_FIRST flag on certificate stores when it is available.

- bpo-23576: Avoid stalling in SSL reads when EOF has been reached in the SSL layer but the underlying connection hasn’t been closed.

- bpo-23504: Added an __all__ to the types module.

- bpo-23563: Optimized utility functions in urllib.parse.

- bpo-7830: Flatten nested functools.partial.

- bpo-20204: Added the __module__ attribute to _tkinter classes.

- bpo-19980: Improved help() for non-recognized strings. help(‘’) now shows the help on str. help(‘help’) now shows the help on help(). Original patch by Mark Lawrence.

- bpo-23521: Corrected pure python implementation of timedelta division.

  Eliminated OverflowError from `timedelta * float` for some floats; Corrected rounding in timedelta true division.

- bpo-21619: Popen objects no longer leave a zombie after exit in the with statement if the pipe was broken. Patch by Martin Panter.

- bpo-22936: Make it possible to show local variables in tracebacks for both the traceback module and unittest.

- bpo-15955: Add an option to limit the output size in bz2.decompress(). Patch by Nikolaus Rath.

- bpo-6639: Module-level turtle functions no longer raise TclError after closing the window.

- bpo-814253: Group references and conditional group references now work in lookbehind assertions in regular expressions. (See also: bpo-9179)

- bpo-23215: Multibyte codecs with custom error handlers that ignores errors consumed too much memory and raised SystemError or MemoryError. Original patch by Aleksi Torhamo.

- bpo-5700: io.FileIO() called flush() after closing the file. flush() was not called in close() if closefd=False.

- bpo-23374: Fixed pydoc failure with non-ASCII files when stdout encoding differs from file system encoding (e.g. on Mac OS).

- bpo-23481: Remove RC4 from the SSL module’s default cipher list.

- bpo-21548: Fix pydoc.synopsis() and pydoc.apropos() on modules with empty docstrings.

- bpo-22885: Fixed arbitrary code execution vulnerability in the dbm.dumb module. Original patch by Claudiu Popa.

- bpo-23239: ssl.match_hostname() now supports matching of IP addresses.

- bpo-23146: Fix mishandling of absolute Windows paths with forward slashes in pathlib.

- bpo-23096: Pickle representation of floats with protocol 0 now is the same for both Python and C implementations.

- bpo-19105: pprint now more efficiently uses free space at the right.

- bpo-14910: Add allow_abbrev parameter to argparse.ArgumentParser. Patch by Jonathan Paugh, Steven Bethard, paul j3 and Daniel Eriksson.

- bpo-21717: tarfile.open() now supports ‘x’ (exclusive creation) mode.

- bpo-23344: marshal.dumps() is now 20-25% faster on average.

- bpo-20416: marshal.dumps() with protocols 3 and 4 is now 40-50% faster on average.

- bpo-23421: Fixed compression in tarfile CLI. Patch by wdv4758h.

- bpo-23367: Fix possible overflows in the unicodedata module.

- bpo-23361: Fix possible overflow in Windows subprocess creation code.

- logging.handlers.QueueListener now takes a respect_handler_level keyword argument which, if set to True, will pass messages to handlers taking handler levels into account.

- bpo-19705: turtledemo now has a visual sorting algorithm demo. Original patch from Jason Yeo.

- bpo-23801: Fix issue where cgi.FieldStorage did not always ignore the entire preamble to a multipart body.

### Build

- bpo-23445: pydebug builds now use “gcc -Og” where possible, to make the resulting executable faster.
- bpo-23686: Update OS X 10.5 installer build to use OpenSSL 1.0.2a.

### C API

- bpo-20204: Deprecation warning is now raised for builtin types without the __module__ attribute.

### Windows

- bpo-23465: Implement PEP 486 - Make the Python Launcher aware of virtual environments. Patch by Paul Moore.
- bpo-23437: Make user scripts directory versioned on Windows. Patch by Paul Moore.

## Python 3.5.0 alpha 1

Release date: 2015-02-08

### Core and Builtins

- bpo-23285: PEP 475 - EINTR handling.
- bpo-22735: Fix many edge cases (including crashes) involving custom mro() implementations.
- bpo-22896: Avoid using PyObject_AsCharBuffer(), PyObject_AsReadBuffer() and PyObject_AsWriteBuffer().
- bpo-21295: Revert some changes (bpo-16795) to AST line numbers and column offsets that constituted a regression.
- bpo-22986: Allow changing an object’s __class__ between a dynamic type and static type in some cases.
- bpo-15859: PyUnicode_EncodeFSDefault(), PyUnicode_EncodeMBCS() and PyUnicode_EncodeCodePage() now raise an exception if the object is not a Unicode object. For PyUnicode_EncodeFSDefault(), it was already the case on platforms other than Windows. Patch written by Campbell Barton.
- bpo-21408: The default __ne__() now returns NotImplemented if __eq__() returned NotImplemented. Original patch by Martin Panter.
- bpo-23321: Fixed a crash in str.decode() when error handler returned replacement string longer than malformed input data.
- bpo-22286: The “backslashreplace” error handlers now works with decoding and translating.
- bpo-23253: Delay-load ShellExecute[AW] in os.startfile for reduced startup overhead on Windows.
- bpo-22038: pyatomic.h now uses stdatomic.h or GCC built-in functions for atomic memory access if available. Patch written by Vitor de Lima and Gustavo Temple.
- bpo-20284: %-interpolation (aka printf) formatting added for bytes and bytearray.
- bpo-23048: Fix jumping out of an infinite while loop in the pdb.
- bpo-20335: bytes constructor now raises TypeError when encoding or errors is specified with non-string argument. Based on patch by Renaud Blanch.
- bpo-22834: If the current working directory ends up being set to a non-existent directory then import will no longer raise FileNotFoundError.
- bpo-22869: Move the interpreter startup & shutdown code to a new dedicated pylifecycle.c module
- bpo-22847: Improve method cache efficiency.
- bpo-22335: Fix crash when trying to enlarge a bytearray to 0x7fffffff bytes on a 32-bit platform.
- bpo-22653: Fix an assertion failure in debug mode when doing a reentrant dict insertion in debug mode.
- bpo-22643: Fix integer overflow in Unicode case operations (upper, lower, title, swapcase, casefold).
- bpo-17636: Circular imports involving relative imports are now supported.
- bpo-22604: Fix assertion error in debug mode when dividing a complex number by (nan+0j).
- bpo-21052: Do not raise ImportWarning when sys.path_hooks or sys.meta_path are set to None.
- bpo-16518: Use ‘bytes-like object required’ in error messages that previously used the far more cryptic “‘x’ does not support the buffer protocol.
- bpo-22470: Fixed integer overflow issues in “backslashreplace”, “xmlcharrefreplace”, and “surrogatepass” error handlers.
- bpo-22540: speed up `PyObject_IsInstance` and `PyObject_IsSubclass` in the common case that the second argument has metaclass `type`.
- bpo-18711: Add a new `PyErr_FormatV` function, similar to `PyErr_Format` but accepting a `va_list` argument.
- bpo-22520: Fix overflow checking when generating the repr of a unicode object.
- bpo-22519: Fix overflow checking in PyBytes_Repr.
- bpo-22518: Fix integer overflow issues in latin-1 encoding.
- bpo-16324: _charset parameter of MIMEText now also accepts email.charset.Charset instances. Initial patch by Claude Paroz.
- bpo-1764286: Fix inspect.getsource() to support decorated functions. Patch by Claudiu Popa.
- bpo-18554: os.__all__ includes posix functions.
- bpo-21391: Use os.path.abspath in the shutil module.
- bpo-11471: avoid generating a JUMP_FORWARD instruction at the end of an if-block if there is no else-clause. Original patch by Eugene Toder.
- bpo-22215: Now ValueError is raised instead of TypeError when str or bytes argument contains not permitted null character or byte.
- bpo-22258: Fix the internal function set_inheritable() on Illumos. This platform exposes the function `ioctl(FIOCLEX)`, but calling it fails with errno is ENOTTY: “Inappropriate ioctl for device”. set_inheritable() now falls back to the slower `fcntl()` (`F_GETFD` and then `F_SETFD`).
- bpo-21389: Displaying the __qualname__ of the underlying function in the repr of a bound method.
- bpo-22206: Using pthread, PyThread_create_key() now sets errno to ENOMEM and returns -1 (error) on integer overflow.
- bpo-20184: Argument Clinic based signature introspection added for 30 of the builtin functions.
- bpo-22116: C functions and methods (of the ‘builtin_function_or_method’ type) can now be weakref’ed. Patch by Wei Wu.
- bpo-22077: Improve index error messages for bytearrays, bytes, lists, and tuples by adding ‘or slices’. Added ‘, not <typename>’ for bytearrays. Original patch by Claudiu Popa.
- bpo-20179: Apply Argument Clinic to bytes and bytearray. Patch by Tal Einat.
- bpo-22082: Clear interned strings in slotdefs.
- Upgrade Unicode database to Unicode 7.0.0.
- bpo-21897: Fix a crash with the f_locals attribute with closure variables when frame.clear() has been called.
- bpo-21205: Add a new `__qualname__` attribute to generator, the qualified name, and use it in the representation of a generator (`repr(gen)`). The default name of the generator (`__name__` attribute) is now get from the function instead of the code. Use `gen.gi_code.co_name` to get the name of the code.
- bpo-21669: With the aid of heuristics in SyntaxError.__init__, the parser now attempts to generate more meaningful (or at least more search engine friendly) error messages when “exec” and “print” are used as statements.
- bpo-21642: In the conditional if-else expression, allow an integer written with no space between itself and the `else` keyword (e.g. `True if 42else False`) to be valid syntax.
- bpo-21523: Fix over-pessimistic computation of the stack effect of some opcodes in the compiler. This also fixes a quadratic compilation time issue noticeable when compiling code with a large number of “and” and “or” operators.
- bpo-21418: Fix a crash in the builtin function super() when called without argument and without current frame (ex: embedded Python).
- bpo-21425: Fix flushing of standard streams in the interactive interpreter.
- bpo-21435: In rare cases, when running finalizers on objects in cyclic trash a bad pointer dereference could occur due to a subtle flaw in internal iteration logic.
- bpo-21377: PyBytes_Concat() now tries to concatenate in-place when the first argument has a reference count of 1. Patch by Nikolaus Rath.
- bpo-20355: -W command line options now have higher priority than the PYTHONWARNINGS environment variable. Patch by Arfrever.
- bpo-21274: Define PATH_MAX for GNU/Hurd in Python/pythonrun.c.
- bpo-20904: Support setting FPU precision on m68k.
- bpo-21209: Fix sending tuples to custom generator objects with the yield from syntax.
- bpo-21193: pow(a, b, c) now raises ValueError rather than TypeError when b is negative. Patch by Josh Rosenberg.
- bpo-21176: PEP 465: Add the ‘@’ operator for matrix multiplication.
- bpo-21134: Fix segfault when str is called on an uninitialized UnicodeEncodeError, UnicodeDecodeError, or UnicodeTranslateError object.
- bpo-19537: Fix PyUnicode_DATA() alignment under m68k. Patch by Andreas Schwab.
- bpo-20929: Add a type cast to avoid shifting a negative number.
- bpo-20731: Properly position in source code files even if they are opened in text mode. Patch by Serhiy Storchaka.
- bpo-20637: Key-sharing now also works for instance dictionaries of subclasses. Patch by Peter Ingebretson.
- bpo-8297: Attributes missing from modules now include the module name in the error text. Original patch by ysj.ray.
- bpo-19995: %c, %o, %x, and %X now raise TypeError on non-integer input.
- bpo-19655: The ASDL parser - used by the build process to generate code for managing the Python AST in C - was rewritten. The new parser is self contained and does not require to carry long the spark.py parser-generator library; spark.py was removed from the source base.
- bpo-12546: Allow `\x00` to be used as a fill character when using str, int, float, and complex __format__ methods.
- bpo-20480: Add ipaddress.reverse_pointer. Patch by Leon Weber.
- bpo-13598: Modify string.Formatter to support auto-numbering of replacement fields. It now matches the behavior of str.format() in this regard. Patches by Phil Elson and Ramchandra Apte.
- bpo-8931: Make alternate formatting (‘#’) for type ‘c’ raise an exception. In versions prior to 3.5, ‘#’ with ‘c’ had no effect. Now specifying it is an error. Patch by Torsten Landschoff.
- bpo-23165: Perform overflow checks before allocating memory in the _Py_char2wchar function.

### Library

- bpo-23399: pyvenv creates relative symlinks where possible.
- bpo-20289: cgi.FieldStorage() now supports the context management protocol.
- bpo-13128: Print response headers for CONNECT requests when debuglevel > 0. Patch by Demian Brecht.
- bpo-15381: Optimized io.BytesIO to make less allocations and copyings.
- bpo-22818: Splitting on a pattern that could match an empty string now raises a warning. Patterns that can only match empty strings are now rejected.
- bpo-23099: Closing io.BytesIO with exported buffer is rejected now to prevent corrupting exported buffer.
- bpo-23326: Removed __ne__ implementations. Since fixing default __ne__ implementation in bpo-21408 they are redundant.
- bpo-23363: Fix possible overflow in itertools.permutations.
- bpo-23364: Fix possible overflow in itertools.product.
- bpo-23366: Fixed possible integer overflow in itertools.combinations.
- bpo-23369: Fixed possible integer overflow in _json.encode_basestring_ascii.
- bpo-23353: Fix the exception handling of generators in PyEval_EvalFrameEx(). At entry, save or swap the exception state even if PyEval_EvalFrameEx() is called with throwflag=0. At exit, the exception state is now always restored or swapped, not only if why is WHY_YIELD or WHY_RETURN. Patch co-written with Antoine Pitrou.
- bpo-14099: Restored support of writing ZIP files to tellable but non-seekable streams.
- bpo-14099: Writing to ZipFile and reading multiple ZipExtFiles is threadsafe now.
- bpo-19361: JSON decoder now raises JSONDecodeError instead of ValueError.
- bpo-18518: timeit now rejects statements which can’t be compiled outside a function or a loop (e.g. “return” or “break”).
- bpo-23094: Fixed readline with frames in Python implementation of pickle.
- bpo-23268: Fixed bugs in the comparison of ipaddress classes.
- bpo-21408: Removed incorrect implementations of __ne__() which didn’t returned NotImplemented if __eq__() returned NotImplemented. The default __ne__() now works correctly.
- bpo-19996: `email.feedparser.FeedParser` now handles (malformed) headers with no key rather than assuming the body has started.
- bpo-20188: Support Application-Layer Protocol Negotiation (ALPN) in the ssl module.
- bpo-23133: Pickling of ipaddress objects now produces more compact and portable representation.
- bpo-23248: Update ssl error codes from latest OpenSSL git master.
- bpo-23266: Much faster implementation of ipaddress.collapse_addresses() when there are many non-consecutive addresses.
- bpo-23098: 64-bit dev_t is now supported in the os module.
- bpo-21817: When an exception is raised in a task submitted to a ProcessPoolExecutor, the remote traceback is now displayed in the parent process. Patch by Claudiu Popa.
- bpo-15955: Add an option to limit output size when decompressing LZMA data. Patch by Nikolaus Rath and Martin Panter.
- bpo-23250: In the http.cookies module, capitalize “HttpOnly” and “Secure” as they are written in the standard.
- bpo-23063: In the distutils’ check command, fix parsing of reST with code or code-block directives.
- bpo-23209: selectors.BaseSelector.get_key() now raises a RuntimeError if the selector is closed. And selectors.BaseSelector.close() now clears its internal reference to the selector mapping to break a reference cycle. Initial patch written by Martin Richard. (See also: bpo-23225)
- bpo-17911: Provide a way to seed the linecache for a PEP-302 module without actually loading the code.
- bpo-17911: Provide a new object API for traceback, including the ability to not lookup lines at all until the traceback is actually rendered, without any trace of the original objects being kept alive.
- bpo-19777: Provide a home() classmethod on Path objects. Contributed by Victor Salgado and Mayank Tripathi.
- bpo-23206: Make `json.dumps(..., ensure_ascii=False)` as fast as the default case of `ensure_ascii=True`. Patch by Naoki Inada.
- bpo-23185: Add math.inf and math.nan constants.
- bpo-23186: Add ssl.SSLObject.shared_ciphers() and ssl.SSLSocket.shared_ciphers() to fetch the client’s list ciphers sent at handshake.
- bpo-23143: Remove compatibility with OpenSSLs older than 0.9.8.
- bpo-23132: Improve performance and introspection support of comparison methods created by functool.total_ordering.
- bpo-19776: Add an expanduser() method on Path objects.
- bpo-23112: Fix SimpleHTTPServer to correctly carry the query string and fragment when it redirects to add a trailing slash.
- bpo-21793: Added http.HTTPStatus enums (i.e. HTTPStatus.OK, HTTPStatus.NOT_FOUND). Patch by Demian Brecht.
- bpo-23093: In the io, module allow more operations to work on detached streams.
- bpo-23111: In the ftplib, make ssl.PROTOCOL_SSLv23 the default protocol version.
- bpo-22585: On OpenBSD 5.6 and newer, os.urandom() now calls getentropy(), instead of reading /dev/urandom, to get pseudo-random bytes.
- bpo-19104: pprint now produces evaluable output for wrapped strings.
- bpo-23071: Added missing names to codecs.__all__. Patch by Martin Panter.
- bpo-22783: Pickling now uses the NEWOBJ opcode instead of the NEWOBJ_EX opcode if possible.
- bpo-15513: Added a __sizeof__ implementation for pickle classes.
- bpo-19858: pickletools.optimize() now aware of the MEMOIZE opcode, can produce more compact result and no longer produces invalid output if input data contains MEMOIZE opcodes together with PUT or BINPUT opcodes.
- bpo-22095: Fixed HTTPConnection.set_tunnel with default port. The port value in the host header was set to “None”. Patch by Demian Brecht.
- bpo-23016: A warning no longer produces an AttributeError when the program is run with pythonw.exe.
- bpo-21775: shutil.copytree(): fix crash when copying to VFAT. An exception handler assumed that OSError objects always have a ‘winerror’ attribute. That is not the case, so the exception handler itself raised AttributeError when run on Linux (and, presumably, any other non-Windows OS). Patch by Greg Ward.
- bpo-1218234: Fix inspect.getsource() to load updated source of reloaded module. Initial patch by Berker Peksag.
- bpo-21740: Support wrapped callables in doctest. Patch by Claudiu Popa.
- bpo-23009: Make sure selectors.EpollSelecrtor.select() works when no FD is registered.
- bpo-22959: In the constructor of http.client.HTTPSConnection, prefer the context’s check_hostname attribute over the check_hostname parameter.
- bpo-22696: Add function `sys.is_finalizing()` to know about interpreter shutdown.
- bpo-16043: Add a default limit for the amount of data xmlrpclib.gzip_decode will return. This resolves CVE-2013-1753.
- bpo-14099: ZipFile.open() no longer reopen the underlying file. Objects returned by ZipFile.open() can now operate independently of the ZipFile even if the ZipFile was created by passing in a file-like object as the first argument to the constructor.
- bpo-22966: Fix __pycache__ pyc file name clobber when pyc_compile is asked to compile a source file containing multiple dots in the source file name.
- bpo-21971: Update turtledemo doc and add module to the index.
- bpo-21032: Fixed socket leak if HTTPConnection.getresponse() fails. Original patch by Martin Panter.
- bpo-22407: Deprecated the use of re.LOCALE flag with str patterns or re.ASCII. It was newer worked.
- bpo-22902: The “ip” command is now used on Linux to determine MAC address in uuid.getnode(). Pach by Bruno Cauet.
- bpo-22960: Add a context argument to xmlrpclib.ServerProxy constructor.
- bpo-22389: Add contextlib.redirect_stderr().
- bpo-21356: Make ssl.RAND_egd() optional to support LibreSSL. The availability of the function is checked during the compilation. Patch written by Bernard Spil.
- bpo-22915: SAX parser now supports files opened with file descriptor or bytes path.
- bpo-22609: Constructors and update methods of mapping classes in the collections module now accept the self keyword argument.
- bpo-22940: Add readline.append_history_file.
- bpo-19676: Added the “namereplace” error handler.
- bpo-22788: Add context parameter to logging.handlers.HTTPHandler.
- bpo-22921: Allow SSLContext to take the hostname parameter even if OpenSSL doesn’t support SNI.
- bpo-22894: TestCase.subTest() would cause the test suite to be stopped when in failfast mode, even in the absence of failures.
- bpo-22796: HTTP cookie parsing is now stricter, in order to protect against potential injection attacks.
- bpo-22370: Windows detection in pathlib is now more robust.
- bpo-22841: Reject coroutines in asyncio add_signal_handler(). Patch by Ludovic.Gasc.
- bpo-19494: Added urllib.request.HTTPBasicPriorAuthHandler. Patch by Matej Cepl.
- bpo-22578: Added attributes to the re.error class.
- bpo-22849: Fix possible double free in the io.TextIOWrapper constructor.
- bpo-12728: Different Unicode characters having the same uppercase but different lowercase are now matched in case-insensitive regular expressions.
- bpo-22821: Fixed fcntl() with integer argument on 64-bit big-endian platforms.
- bpo-21650: Add an `--sort-keys` option to json.tool CLI.
- bpo-22824: Updated reprlib output format for sets to use set literals. Patch contributed by Berker Peksag.
- bpo-22824: Updated reprlib output format for arrays to display empty arrays without an unnecessary empty list. Suggested by Serhiy Storchaka.
- bpo-22406: Fixed the uu_codec codec incorrectly ported to 3.x. Based on patch by Martin Panter.
- bpo-17293: uuid.getnode() now determines MAC address on AIX using netstat. Based on patch by Aivars Kalvāns.
- bpo-22769: Fixed ttk.Treeview.tag_has() when called without arguments.
- bpo-22417: Verify certificates by default in httplib (PEP 476).
- bpo-22775: Fixed unpickling of http.cookies.SimpleCookie with protocol 2 and above. Patch by Tim Graham.
- bpo-22776: Brought excluded code into the scope of a try block in SysLogHandler.emit().
- bpo-22665: Add missing get_terminal_size and SameFileError to shutil.__all__.
- bpo-6623: Remove deprecated Netrc class in the ftplib module. Patch by Matt Chaput.
- bpo-17381: Fixed handling of case-insensitive ranges in regular expressions.
- bpo-22410: Module level functions in the re module now cache compiled locale-dependent regular expressions taking into account the locale.
- bpo-22759: Query methods on pathlib.Path() (exists(), is_dir(), etc.) now return False when the underlying stat call raises NotADirectoryError.
- bpo-8876: distutils now falls back to copying files when hard linking doesn’t work. This allows use with special filesystems such as VirtualBox shared folders.
- bpo-22217: Implemented reprs of classes in the zipfile module.
- bpo-22457: Honour load_tests in the start_dir of discovery.
- bpo-18216: gettext now raises an error when a .mo file has an unsupported major version number. Patch by Aaron Hill.
- bpo-13918: Provide a locale.delocalize() function which can remove locale-specific number formatting from a string representing a number, without then converting it to a specific type. Patch by Cédric Krier.
- bpo-22676: Make the pickling of global objects which don’t have a __module__ attribute less slow.
- bpo-18853: Fixed ResourceWarning in shlex.__nain__.
- bpo-9351: Defaults set with set_defaults on an argparse subparser are no longer ignored when also set on the parent parser.
- bpo-7559: unittest test loading ImportErrors are reported as import errors with their import exception rather than as attribute errors after the import has already failed.
- bpo-19746: Make it possible to examine the errors from unittest discovery without executing the test suite. The new `errors` attribute on TestLoader exposes these non-fatal errors encountered during discovery.
- bpo-21991: Make email.headerregistry’s header ‘params’ attributes be read-only (MappingProxyType). Previously the dictionary was modifiable but a new one was created on each access of the attribute.
- bpo-22638: SSLv3 is now disabled throughout the standard library. It can still be enabled by instantiating a SSLContext manually.
- bpo-22641: In asyncio, the default SSL context for client connections is now created using ssl.create_default_context(), for stronger security.
- bpo-17401: Include closefd in io.FileIO repr.
- bpo-21338: Add silent mode for compileall. quiet parameters of compile_{dir, file, path} functions now have a multilevel value. Also, -q option of the CLI now have a multilevel value. Patch by Thomas Kluyver.
- bpo-20152: Convert the array and cmath modules to Argument Clinic.
- bpo-18643: Add socket.socketpair() on Windows.
- bpo-22435: Fix a file descriptor leak when socketserver bind fails.
- bpo-13096: Fixed segfault in CTypes POINTER handling of large values.
- bpo-11694: Raise ConversionError in xdrlib as documented. Patch by Filip Gruszczyński and Claudiu Popa.
- bpo-19380: Optimized parsing of regular expressions.
- bpo-1519638: Now unmatched groups are replaced with empty strings in re.sub() and re.subn().
- bpo-18615: sndhdr.what/whathdr now return a namedtuple.
- bpo-22462: Fix pyexpat’s creation of a dummy frame to make it appear in exception tracebacks.
- bpo-21965: Add support for in-memory SSL to the ssl module. Patch by Geert Jansen.
- bpo-21173: Fix len() on a WeakKeyDictionary when .clear() was called with an iterator alive.
- bpo-11866: Eliminated race condition in the computation of names for new threads.
- bpo-21905: Avoid RuntimeError in pickle.whichmodule() when sys.modules is mutated while iterating. Patch by Olivier Grisel.
- bpo-11271: concurrent.futures.Executor.map() now takes a chunksize argument to allow batching of tasks in child processes and improve performance of ProcessPoolExecutor. Patch by Dan O’Reilly.
- bpo-21883: os.path.join() and os.path.relpath() now raise a TypeError with more helpful error message for unsupported or mismatched types of arguments.
- bpo-22219: The zipfile module CLI now adds entries for directories (including empty directories) in ZIP file.
- bpo-22449: In the ssl.SSLContext.load_default_certs, consult the environmental variables SSL_CERT_DIR and SSL_CERT_FILE on Windows.
- bpo-22508: The email.__version__ variable has been removed; the email code is no longer shipped separately from the stdlib, and __version__ hasn’t been updated in several releases.
- bpo-20076: Added non derived UTF-8 aliases to locale aliases table.
- bpo-20079: Added locales supported in glibc 2.18 to locale alias table.
- bpo-20218: Added convenience methods read_text/write_text and read_bytes/ write_bytes to pathlib.Path objects.
- bpo-22396: On 32-bit AIX platform, don’t expose os.posix_fadvise() nor os.posix_fallocate() because their prototypes in system headers are wrong.
- bpo-22517: When an io.BufferedRWPair object is deallocated, clear its weakrefs.
- bpo-22437: Number of capturing groups in regular expression is no longer limited by 100.
- bpo-17442: InteractiveInterpreter now displays the full chained traceback in its showtraceback method, to match the built in interactive interpreter.
- bpo-23392: Added tests for marshal C API that works with FILE*.
- bpo-10510: distutils register and upload methods now use HTML standards compliant CRLF line endings.
- bpo-9850: Fixed macpath.join() for empty first component. Patch by Oleg Oshmyan.
- bpo-5309: distutils’ build and build_ext commands now accept a `-j` option to enable parallel building of extension modules.
- bpo-22448: Improve canceled timer handles cleanup to prevent unbound memory usage. Patch by Joshua Moore-Oliva.
- bpo-22427: TemporaryDirectory no longer attempts to clean up twice when used in the with statement in generator.
- bpo-22362: Forbidden ambiguous octal escapes out of range 0-0o377 in regular expressions.
- bpo-20912: Now directories added to ZIP file have correct Unix and MS-DOS directory attributes.
- bpo-21866: ZipFile.close() no longer writes ZIP64 central directory records if allowZip64 is false.
- bpo-22278: Fix urljoin problem with relative urls, a regression observed after changes to issue22118 were submitted.
- bpo-22415: Fixed debugging output of the GROUPREF_EXISTS opcode in the re module. Removed trailing spaces in debugging output.
- bpo-22423: Unhandled exception in thread no longer causes unhandled AttributeError when sys.stderr is None.
- bpo-21332: Ensure that `bufsize=1` in subprocess.Popen() selects line buffering, rather than block buffering. Patch by Akira Li.
- bpo-21091: Fix API bug: email.message.EmailMessage.is_attachment is now a method.
- bpo-21079: Fix email.message.EmailMessage.is_attachment to return the correct result when the header has parameters as well as a value.
- bpo-22247: Add NNTPError to nntplib.__all__.
- bpo-22366: urllib.request.urlopen will accept a context object (SSLContext) as an argument which will then be used for HTTPS connection. Patch by Alex Gaynor.
- bpo-4180: The warnings registries are now reset when the filters are modified.
- bpo-22419: Limit the length of incoming HTTP request in wsgiref server to 65536 bytes and send a 414 error code for higher lengths. Patch contributed by Devin Cook.
- Lax cookie parsing in http.cookies could be a security issue when combined with non-standard cookie handling in some Web browsers. Reported by Sergey Bobrov.
- bpo-20537: logging methods now accept an exception instance as well as a Boolean value or exception tuple. Thanks to Yury Selivanov for the patch.
- bpo-22384: An exception in Tkinter callback no longer crashes the program when it is run with pythonw.exe.
- bpo-22168: Prevent turtle AttributeError with non-default Canvas on OS X.
- bpo-21147: sqlite3 now raises an exception if the request contains a null character instead of truncating it. Based on patch by Victor Stinner.
- bpo-13968: The glob module now supports recursive search in subdirectories using the `**` pattern.
- bpo-21951: Fixed a crash in Tkinter on AIX when called Tcl command with empty string or tuple argument.
- bpo-21951: Tkinter now most likely raises MemoryError instead of crash if the memory allocation fails.
- bpo-22338: Fix a crash in the json module on memory allocation failure.
- bpo-12410: imaplib.IMAP4 now supports the context management protocol. Original patch by Tarek Ziadé.
- bpo-21270: We now override tuple methods in mock.call objects so that they can be used as normal call attributes.
- bpo-16662: load_tests() is now unconditionally run when it is present in a package’s __init__.py. TestLoader.loadTestsFromModule() still accepts use_load_tests, but it is deprecated and ignored. A new keyword-only attribute `pattern` is added and documented. Patch given by Robert Collins, tweaked by Barry Warsaw.
- bpo-22226: First letter no longer is stripped from the “status” key in the result of Treeview.heading().
- bpo-19524: Fixed resource leak in the HTTP connection when an invalid response is received. Patch by Martin Panter.
- bpo-20421: Add a .version() method to SSL sockets exposing the actual protocol version in use.
- bpo-19546: configparser exceptions no longer expose implementation details. Chained KeyErrors are removed, which leads to cleaner tracebacks. Patch by Claudiu Popa.
- bpo-22051: turtledemo no longer reloads examples to re-run them. Initialization of variables and gui setup should be done in main(), which is called each time a demo is run, but not on import.
- bpo-21933: Turtledemo users can change the code font size with a menu selection or control(command) ‘-‘ or ‘+’ or control-mousewheel. Original patch by Lita Cho.
- bpo-21597: The separator between the turtledemo text pane and the drawing canvas can now be grabbed and dragged with a mouse. The code text pane can be widened to easily view or copy the full width of the text. The canvas can be widened on small screens. Original patches by Jan Kanis and Lita Cho.
- bpo-18132: Turtledemo buttons no longer disappear when the window is shrunk. Original patches by Jan Kanis and Lita Cho.
- bpo-22043: time.monotonic() is now always available. `threading.Lock.acquire()`, `threading.RLock.acquire()` and socket operations now use a monotonic clock, instead of the system clock, when a timeout is used.
- bpo-21527: Add a default number of workers to ThreadPoolExecutor equal to 5 times the number of CPUs. Patch by Claudiu Popa.
- bpo-22216: smtplib now resets its state more completely after a quit. The most obvious consequence of the previous behavior was a STARTTLS failure during a connect/starttls/quit/connect/starttls sequence.
- bpo-22098: ctypes’ BigEndianStructure and LittleEndianStructure now define an empty __slots__ so that subclasses don’t always get an instance dict. Patch by Claudiu Popa.
- bpo-22185: Fix an occasional RuntimeError in threading.Condition.wait() caused by mutation of the waiters queue without holding the lock. Patch by Doug Zongker.
- bpo-22287: On UNIX, _PyTime_gettimeofday() now uses clock_gettime(CLOCK_REALTIME) if available. As a side effect, Python now depends on the librt library on Solaris and on Linux (only with glibc older than 2.17).
- bpo-22182: Use e.args to unpack exceptions correctly in distutils.file_util.move_file. Patch by Claudiu Popa.
- The webbrowser module now uses subprocess’s start_new_session=True rather than a potentially risky preexec_fn=os.setsid call.
- bpo-22042: signal.set_wakeup_fd(fd) now raises an exception if the file descriptor is in blocking mode.
- bpo-16808: inspect.stack() now returns a named tuple instead of a tuple. Patch by Daniel Shahaf.
- bpo-22236: Fixed Tkinter images copying operations in NoDefaultRoot mode.
- bpo-2527: Add a globals argument to timeit functions, in order to override the globals namespace in which the timed code is executed. Patch by Ben Roberts.
- bpo-22118: Switch urllib.parse to use RFC 3986 semantics for the resolution of relative URLs, rather than RFCs 1808 and 2396. Patch by Demian Brecht.
- bpo-21549: Added the “members” parameter to TarFile.list().
- bpo-19628: Allow compileall recursion depth to be specified with a -r option.
- bpo-15696: Add a __sizeof__ implementation for mmap objects on Windows.
- bpo-22068: Avoided reference loops with Variables and Fonts in Tkinter.
- bpo-22165: SimpleHTTPRequestHandler now supports undecodable file names.
- bpo-15381: Optimized line reading in io.BytesIO.
- bpo-8797: Raise HTTPError on failed Basic Authentication immediately. Initial patch by Sam Bull.
- bpo-20729: Restored the use of lazy iterkeys()/itervalues()/iteritems() in the mailbox module.
- bpo-21448: Changed FeedParser feed() to avoid O(N**2) behavior when parsing long line. Original patch by Raymond Hettinger.
- bpo-22184: The functools LRU Cache decorator factory now gives an earlier and clearer error message when the user forgets the required parameters.
- bpo-17923: glob() patterns ending with a slash no longer match non-dirs on AIX. Based on patch by Delhallt.
- bpo-21725: Added support for RFC 6531 (SMTPUTF8) in smtpd.
- bpo-22176: Update the ctypes module’s libffi to v3.1. This release adds support for the Linux AArch64 and POWERPC ELF ABIv2 little endian architectures.
- bpo-5411: Added support for the “xztar” format in the shutil module.
- bpo-21121: Don’t force 3rd party C extensions to be built with -Werror=declaration-after-statement.
- bpo-21975: Fixed crash when using uninitialized sqlite3.Row (in particular when unpickling pickled sqlite3.Row). sqlite3.Row is now initialized in the __new__() method.
- bpo-20170: Convert posixmodule to use Argument Clinic.
- bpo-21539: Add an exists_ok argument to `Pathlib.mkdir()` to mimic `mkdir -p` and `os.makedirs()` functionality. When true, ignore FileExistsErrors. Patch by Berker Peksag.
- bpo-22127: Bypass IDNA for pure-ASCII host names in the socket module (in particular for numeric IPs).
- bpo-21047: set the default value for the convert_charrefs argument of HTMLParser to True. Patch by Berker Peksag.
- Add an __all__ to html.entities.
- bpo-15114: the strict mode and argument of HTMLParser, HTMLParser.error, and the HTMLParserError exception have been removed.
- bpo-22085: Dropped support of Tk 8.3 in Tkinter.
- bpo-21580: Now Tkinter correctly handles bytes arguments passed to Tk. In particular this allows initializing images from binary data.
- bpo-22003: When initialized from a bytes object, io.BytesIO() now defers making a copy until it is mutated, improving performance and memory use on some use cases. Patch by David Wilson.
- bpo-22018: On Windows, signal.set_wakeup_fd() now also supports sockets. A side effect is that Python depends to the WinSock library.
- bpo-22054: Add os.get_blocking() and os.set_blocking() functions to get and set the blocking mode of a file descriptor (False if the O_NONBLOCK flag is set, True otherwise). These functions are not available on Windows.
- bpo-17172: Make turtledemo start as active on OS X even when run with subprocess. Patch by Lita Cho.
- bpo-21704: Fix build error for _multiprocessing when semaphores are not available. Patch by Arfrever Frehtes Taifersar Arahesis.
- bpo-20173: Convert sha1, sha256, sha512 and md5 to ArgumentClinic. Patch by Vajrasky Kok.
- Fix repr(_socket.socket) on Windows 64-bit: don’t fail with OverflowError on closed socket. repr(socket.socket) already works fine.
- bpo-22033: Reprs of most Python implemented classes now contain actual class name instead of hardcoded one.
- bpo-21947: The dis module can now disassemble generator-iterator objects based on their gi_code attribute. Patch by Clement Rouault.
- bpo-16133: The asynchat.async_chat.handle_read() method now ignores BlockingIOError exceptions.
- bpo-22044: Fixed premature DECREF in call_tzinfo_method. Patch by Tom Flanagan.
- bpo-19884: readline: Disable the meta modifier key if stdout is not a terminal to not write the ANSI sequence `"\033[1034h"` into stdout. This sequence is used on some terminal (ex: TERM=xterm-256color”) to enable support of 8 bit characters.
- bpo-4350: Removed a number of out-of-dated and non-working for a long time Tkinter methods.
- bpo-6167: Scrollbar.activate() now returns the name of active element if the argument is not specified. Scrollbar.set() now always accepts only 2 arguments.
- bpo-15275: Clean up and speed up the ntpath module.
- bpo-21888: plistlib’s load() and loads() now work if the fmt parameter is specified.
- bpo-22032: __qualname__ instead of __name__ is now always used to format fully qualified class names of Python implemented classes.
- bpo-22031: Reprs now always use hexadecimal format with the “0x” prefix when contain an id in form ” at 0x…”.
- bpo-22018: signal.set_wakeup_fd() now raises an OSError instead of a ValueError on `fstat()` failure.
- bpo-21044: tarfile.open() now handles fileobj with an integer ‘name’ attribute. Based on patch by Antoine Pietri.
- bpo-21966: Respect -q command-line option when code module is ran.
- bpo-19076: Don’t pass the redundant ‘file’ argument to self.error().
- bpo-16382: Improve exception message of warnings.warn() for bad category. Initial patch by Phil Elson.
- bpo-21932: os.read() now uses a `Py_ssize_t()` type instead of `int` for the size to support reading more than 2 GB at once. On Windows, the size is truncated to INT_MAX. As any call to os.read(), the OS may read less bytes than the number of requested bytes.
- bpo-21942: Fixed source file viewing in pydoc’s server mode on Windows.
- bpo-11259: asynchat.async_chat().set_terminator() now raises a ValueError if the number of received bytes is negative.
- bpo-12523: asynchat.async_chat.push() now raises a TypeError if it doesn’t get a bytes string
- bpo-21707: Add missing kwonlyargcount argument to ModuleFinder.replace_paths_in_code().
- bpo-20639: calling Path.with_suffix(‘’) allows removing the suffix again. Patch by July Tikhonov.
- bpo-21714: Disallow the construction of invalid paths using Path.with_name(). Original patch by Antony Lee.
- bpo-15014: Added ‘auth’ method to smtplib to make implementing auth mechanisms simpler, and used it internally in the login method.
- bpo-21151: Fixed a segfault in the winreg module when `None` is passed as a `REG_BINARY` value to SetValueEx. Patch by John Ehresman.
- bpo-21090: io.FileIO.readall() does not ignore I/O errors anymore. Before, it ignored I/O errors if at least the first C call read() succeed.
- bpo-5800: headers parameter of wsgiref.headers.Headers is now optional. Initial patch by Pablo Torres Navarrete and SilentGhost.
- bpo-21781: ssl.RAND_add() now supports strings longer than 2 GB.
- bpo-21679: Prevent extraneous fstat() calls during open(). Patch by Bohuslav Kabrda.
- bpo-21863: cProfile now displays the module name of C extension functions, in addition to their own name.
- bpo-11453: asyncore: emit a ResourceWarning when an unclosed file_wrapper object is destroyed. The destructor now closes the file if needed. The close() method can now be called twice: the second call does nothing.
- bpo-21858: Better handling of Python exceptions in the sqlite3 module.
- bpo-21476: Make sure the email.parser.BytesParser TextIOWrapper is discarded after parsing, so the input file isn’t unexpectedly closed.
- bpo-20295: imghdr now recognizes OpenEXR format images.
- bpo-21729: Used the “with” statement in the dbm.dumb module to ensure files closing. Patch by Claudiu Popa.
- bpo-21491: socketserver: Fix a race condition in child processes reaping.
- bpo-21719: Added the `st_file_attributes` field to os.stat_result on Windows.
- bpo-21832: Require named tuple inputs to be exact strings.
- bpo-21722: The distutils “upload” command now exits with a non-zero return code when uploading fails. Patch by Martin Dengler.
- bpo-21723: asyncio.Queue: support any type of number (ex: float) for the maximum size. Patch written by Vajrasky Kok.
- bpo-21711: support for “site-python” directories has now been removed from the site module (it was deprecated in 3.4).
- bpo-17552: new socket.sendfile() method allowing a file to be sent over a socket by using high-performance os.sendfile() on UNIX. Patch by Giampaolo Rodola’.
- bpo-18039: dbm.dump.open() now always creates a new database when the flag has the value ‘n’. Patch by Claudiu Popa.
- bpo-21326: Add a new is_closed() method to asyncio.BaseEventLoop. run_forever() and run_until_complete() methods of asyncio.BaseEventLoop now raise an exception if the event loop was closed.
- bpo-21766: Prevent a security hole in CGIHTTPServer by URL unquoting paths before checking for a CGI script at that path.
- bpo-21310: Fixed possible resource leak in failed open().
- bpo-21256: Printout of keyword args should be in deterministic order in a mock function call. This will help to write better doctests.
- bpo-21677: Fixed chaining nonnormalized exceptions in io close() methods.
- bpo-11709: Fix the pydoc.help function to not fail when sys.stdin is not a valid file.
- bpo-21515: tempfile.TemporaryFile now uses os.O_TMPFILE flag is available.
- bpo-13223: Fix pydoc.writedoc so that the HTML documentation for methods that use ‘self’ in the example code is generated correctly.
- bpo-21463: In urllib.request, fix pruning of the FTP cache.
- bpo-21618: The subprocess module could fail to close open fds that were inherited by the calling process and already higher than POSIX resource limits would otherwise allow. On systems with a functioning /proc/self/fd or /dev/fd interface the max is now ignored and all fds are closed.
- bpo-20383: Introduce importlib.util.module_from_spec() as the preferred way to create a new module.
- bpo-21552: Fixed possible integer overflow of too long string lengths in the tkinter module on 64-bit platforms.
- bpo-14315: The zipfile module now ignores extra fields in the central directory that are too short to be parsed instead of letting a struct.unpack error bubble up as this “bad data” appears in many real world zip files in the wild and is ignored by other zip tools.
- bpo-13742: Added “key” and “reverse” parameters to heapq.merge(). (First draft of patch contributed by Simon Sapin.)
- bpo-21402: tkinter.ttk now works when default root window is not set.
- bpo-3015: _tkinter.create() now creates tkapp object with wantobject=1 by default.
- bpo-10203: sqlite3.Row now truly supports sequence protocol. In particular it supports reverse() and negative indices. Original patch by Claudiu Popa.
- bpo-18807: If copying (no symlinks) specified for a venv, then the python interpreter aliases (python, python3) are now created by copying rather than symlinking.
- bpo-20197: Added support for the WebP image type in the imghdr module. Patch by Fabrice Aneche and Claudiu Popa.
- bpo-21513: Speedup some properties of IP addresses (IPv4Address, IPv6Address) such as .is_private or .is_multicast.
- bpo-21137: Improve the repr for threading.Lock() and its variants by showing the “locked” or “unlocked” status. Patch by Berker Peksag.
- bpo-21538: The plistlib module now supports loading of binary plist files when reference or offset size is not a power of two.
- bpo-21455: Add a default backlog to socket.listen().
- bpo-21525: Most Tkinter methods which accepted tuples now accept lists too.
- bpo-22166: With the assistance of a new internal _codecs._forget_codec helping function, test_codecs now clears the encoding caches to avoid the appearance of a reference leak
- bpo-22236: Tkinter tests now don’t reuse default root window. New root window is created for every test class.
- bpo-10744: Fix PEP 3118 format strings on ctypes objects with a nontrivial shape.
- bpo-20826: Optimize ipaddress.collapse_addresses().
- bpo-21487: Optimize ipaddress.summarize_address_range() and ipaddress.{IPv4Network,IPv6Network}.subnets().
- bpo-21486: Optimize parsing of netmasks in ipaddress.IPv4Network and ipaddress.IPv6Network.
- bpo-13916: Disallowed the surrogatepass error handler for non UTF-* encodings.
- bpo-20998: Fixed re.fullmatch() of repeated single character pattern with ignore case. Original patch by Matthew Barnett.
- bpo-21075: fileinput.FileInput now reads bytes from standard stream if binary mode is specified. Patch by Sam Kimbrel.
- bpo-19775: Add a samefile() method to pathlib Path objects. Initial patch by Vajrasky Kok.
- bpo-21226: Set up modules properly in PyImport_ExecCodeModuleObject (and friends).
- bpo-21398: Fix a unicode error in the pydoc pager when the documentation contains characters not encodable to the stdout encoding.
- bpo-16531: ipaddress.IPv4Network and ipaddress.IPv6Network now accept an (address, netmask) tuple argument, so as to easily construct network objects from existing addresses.
- bpo-21156: importlib.abc.InspectLoader.source_to_code() is now a staticmethod.
- bpo-21424: Simplified and optimized heaqp.nlargest() and nmsmallest() to make fewer tuple comparisons.
- bpo-21396: Fix TextIOWrapper(…, write_through=True) to not force a flush() on the underlying binary stream. Patch by akira.
- bpo-18314: Unlink now removes junctions on Windows. Patch by Kim Gräsman
- bpo-21088: Bugfix for curses.window.addch() regression in 3.4.0. In porting to Argument Clinic, the first two arguments were reversed.
- bpo-21407: _decimal: The module now supports function signatures.
- bpo-10650: Remove the non-standard ‘watchexp’ parameter from the Decimal.quantize() method in the Python version. It had never been present in the C version.
- bpo-21469: Reduced the risk of false positives in robotparser by checking to make sure that robots.txt has been read or does not exist prior to returning True in can_fetch().
- bpo-19414: Have the OrderedDict mark deleted links as unusable. This gives an early failure if the link is deleted during iteration.
- bpo-21421: Add __slots__ to the MappingViews ABC. Patch by Josh Rosenberg.
- bpo-21101: Eliminate double hashing in the C speed-up code for collections.Counter().
- bpo-21321: itertools.islice() now releases the reference to the source iterator when the slice is exhausted. Patch by Anton Afanasyev.
- bpo-21057: TextIOWrapper now allows the underlying binary stream’s read() or read1() method to return an arbitrary bytes-like object (such as a memoryview). Patch by Nikolaus Rath.
- bpo-20951: SSLSocket.send() now raises either SSLWantReadError or SSLWantWriteError on a non-blocking socket if the operation would block. Previously, it would return 0. Patch by Nikolaus Rath.
- bpo-13248: removed previously deprecated asyncore.dispatcher __getattr__ cheap inheritance hack.
- bpo-9815: assertRaises now tries to clear references to local variables in the exception’s traceback.
- bpo-19940: ssl.cert_time_to_seconds() now interprets the given time string in the UTC timezone (as specified in RFC 5280), not the local timezone.
- bpo-13204: Calling sys.flags.__new__ would crash the interpreter, now it raises a TypeError.
- bpo-19385: Make operations on a closed dbm.dumb database always raise the same exception.
- bpo-21207: Detect when the os.urandom cached fd has been closed or replaced, and open it anew.
- bpo-21291: subprocess’s Popen.wait() is now thread safe so that multiple threads may be calling wait() or poll() on a Popen instance at the same time without losing the Popen.returncode value.
- bpo-21127: Path objects can now be instantiated from str subclass instances (such as `numpy.str_`).
- bpo-15002: urllib.response object to use _TemporaryFileWrapper (and _TemporaryFileCloser) facility. Provides a better way to handle file descriptor close. Patch contributed by Christian Theune.
- bpo-12220: mindom now raises a custom ValueError indicating it doesn’t support spaces in URIs instead of letting a ‘split’ ValueError bubble up.
- bpo-21068: The ssl.PROTOCOL* constants are now enum members.
- bpo-21276: posixmodule: Don’t define USE_XATTRS on KFreeBSD and the Hurd.
- bpo-21262: New method assert_not_called for Mock. It raises AssertionError if the mock has been called.
- bpo-21238: New keyword argument `unsafe` to Mock. It raises `AttributeError` incase of an attribute startswith assert or assret.
- bpo-20896: ssl.get_server_certificate() now uses PROTOCOL_SSLv23, not PROTOCOL_SSLv3, for maximum compatibility.
- bpo-21239: patch.stopall() didn’t work deterministically when the same name was patched more than once.
- bpo-21203: Updated fileConfig and dictConfig to remove inconsistencies. Thanks to Jure Koren for the patch.
- bpo-21222: Passing name keyword argument to mock.create_autospec now works.
- bpo-21197: Add lib64 -> lib symlink in venvs on 64-bit non-OS X POSIX.
- bpo-17498: Some SMTP servers disconnect after certain errors, violating strict RFC conformance. Instead of losing the error code when we issue the subsequent RSET, smtplib now returns the error code and defers raising the SMTPServerDisconnected error until the next command is issued.
- bpo-17826: setting an iterable side_effect on a mock function created by create_autospec now works. Patch by Kushal Das.
- bpo-7776: Fix `Host:` header and reconnection when using http.client.HTTPConnection.set_tunnel(). Patch by Nikolaus Rath.
- bpo-20968: unittest.mock.MagicMock now supports division. Patch by Johannes Baiter.
- bpo-21529: Fix arbitrary memory access in JSONDecoder.raw_decode with a negative second parameter. Bug reported by Guido Vranken. (See also: CVE-2014-4616)
- bpo-21169: getpass now handles non-ascii characters that the input stream encoding cannot encode by re-encoding using the replace error handler.
- bpo-21171: Fixed undocumented filter API of the rot13 codec. Patch by Berker Peksag.
- bpo-20539: Improved math.factorial error message for large positive inputs and changed exception type (OverflowError -> ValueError) for large negative inputs.
- bpo-21172: isinstance check relaxed from dict to collections.Mapping.
- bpo-21155: asyncio.EventLoop.create_unix_server() now raises a ValueError if path and sock are specified at the same time.
- bpo-21136: Avoid unnecessary normalization of Fractions resulting from power and other operations. Patch by Raymond Hettinger.
- bpo-17621: Introduce importlib.util.LazyLoader.
- bpo-21076: signal module constants were turned into enums. Patch by Giampaolo Rodola’.
- bpo-20636: Improved the repr of Tkinter widgets.
- bpo-19505: The items, keys, and values views of OrderedDict now support reverse iteration using reversed().
- bpo-21149: Improved thread-safety in logging cleanup during interpreter shutdown. Thanks to Devin Jeanpierre for the patch.
- bpo-21058: Fix a leak of file descriptor in `tempfile.NamedTemporaryFile()`, close the file descriptor if `io.open()` fails
- bpo-21200: Return None from pkgutil.get_loader() when __spec__ is missing.
- bpo-21013: Enhance ssl.create_default_context() when used for server side sockets to provide better security by default.
- bpo-20145: `assertRaisesRegex` and `assertWarnsRegex` now raise a TypeError if the second argument is not a string or compiled regex.
- bpo-20633: Replace relative import by absolute import.
- bpo-20980: Stop wrapping exception when using ThreadPool.
- bpo-21082: In os.makedirs, do not set the process-wide umask. Note this changes behavior of makedirs when exist_ok=True.
- bpo-20990: Fix issues found by pyflakes for multiprocessing.
- bpo-21015: SSL contexts will now automatically select an elliptic curve for ECDH key exchange on OpenSSL 1.0.2 and later, and otherwise default to “prime256v1”.
- bpo-21000: Improve the command-line interface of json.tool.
- bpo-20995: Enhance default ciphers used by the ssl module to enable better security and prioritize perfect forward secrecy.
- bpo-20884: Don’t assume that __file__ is defined on importlib.__init__.
- bpo-21499: Ignore __builtins__ in several test_importlib.test_api tests.
- bpo-20627: xmlrpc.client.ServerProxy is now a context manager.
- bpo-19165: The formatter module now raises DeprecationWarning instead of PendingDeprecationWarning.
- bpo-13936: Remove the ability of datetime.time instances to be considered false in boolean contexts.
- bpo-18931: selectors module now supports /dev/poll on Solaris. Patch by Giampaolo Rodola’.
- bpo-19977: When the `LC_TYPE` locale is the POSIX locale (`C` locale), `sys.stdin` and `sys.stdout` are now using the `surrogateescape` error handler, instead of the `strict` error handler.
- bpo-20574: Implement incremental decoder for cp65001 code (Windows code page 65001, Microsoft UTF-8).
- bpo-20879: Delay the initialization of encoding and decoding tables for base32, ascii85 and base85 codecs in the base64 module, and delay the initialization of the unquote_to_bytes() table of the urllib.parse module, to not waste memory if these modules are not used.
- bpo-19157: Include the broadcast address in the usuable hosts for IPv6 in ipaddress.
- bpo-11599: When an external command (e.g. compiler) fails, distutils now prints out the whole command line (instead of just the command name) if the environment variable DISTUTILS_DEBUG is set.
- bpo-4931: distutils should not produce unhelpful “error: None” messages anymore. distutils.util.grok_environment_error is kept but doc-deprecated.
- bpo-20875: Prevent possible gzip “‘read’ is not defined” NameError. Patch by Claudiu Popa.
- bpo-11558: `email.message.Message.attach` now returns a more useful error message if `attach` is called on a message for which `is_multipart` is False.
- bpo-20283: RE pattern methods now accept the string keyword parameters as documented. The pattern and source keyword parameters are left as deprecated aliases.
- bpo-20778: Fix modulefinder to work with bytecode-only modules.
- bpo-20791: copy.copy() now doesn’t make a copy when the input is a bytes object. Initial patch by Peter Otten.
- bpo-19748: On AIX, time.mktime() now raises an OverflowError for year outsize range [1902; 2037].
- bpo-19573: inspect.signature: Use enum for parameter kind constants.
- bpo-20726: inspect.signature: Make Signature and Parameter picklable.
- bpo-17373: Add inspect.Signature.from_callable method.
- bpo-20378: Improve repr of inspect.Signature and inspect.Parameter.
- bpo-20816: Fix inspect.getcallargs() to raise correct TypeError for missing keyword-only arguments. Patch by Jeremiah Lowin.
- bpo-20817: Fix inspect.getcallargs() to fail correctly if more than 3 arguments are missing. Patch by Jeremiah Lowin.
- bpo-6676: Ensure a meaningful exception is raised when attempting to parse more than one XML document per pyexpat xmlparser instance. (Original patches by Hirokazu Yamamoto and Amaury Forgeot d’Arc, with suggested wording by David Gutteridge)
- bpo-21117: Fix inspect.signature to better support functools.partial. Due to the specifics of functools.partial implementation, positional-or-keyword arguments passed as keyword arguments become keyword-only.
- bpo-20334: inspect.Signature and inspect.Parameter are now hashable. Thanks to Antony Lee for bug reports and suggestions.
- bpo-15916: doctest.DocTestSuite returns an empty unittest.TestSuite instead of raising ValueError if it finds no tests
- bpo-21209: Fix asyncio.tasks.CoroWrapper to workaround a bug in yield-from implementation in CPythons prior to 3.4.1.
- asyncio: Add gi_{frame,running,code} properties to CoroWrapper (upstream bpo-163).
- bpo-21311: Avoid exception in _osx_support with non-standard compiler configurations. Patch by John Szakmeister.
- bpo-11571: Ensure that the turtle window becomes the topmost window when launched on OS X.
- bpo-21801: Validate that __signature__ is None or an instance of Signature.
- bpo-21923: Prevent AttributeError in distutils.sysconfig.customize_compiler due to possible uninitialized _config_vars.
- bpo-21323: Fix http.server to again handle scripts in CGI subdirectories, broken by the fix for security bpo-19435. Patch by Zach Byrne.
- bpo-22733: Fix ffi_prep_args not zero-extending argument values correctly on 64-bit Windows.
- bpo-23302: Default to TCP_NODELAY=1 upon establishing an HTTPConnection. Removed use of hard-coded MSS as it’s an optimization that’s no longer needed with Nagle disabled.

### IDLE

- bpo-20577: Configuration of the max line length for the FormatParagraph extension has been moved from the General tab of the Idle preferences dialog to the FormatParagraph tab of the Config Extensions dialog. Patch by Tal Einat.
- bpo-16893: Update Idle doc chapter to match current Idle and add new information.
- bpo-3068: Add Idle extension configuration dialog to Options menu. Changes are written to HOME/.idlerc/config-extensions.cfg. Original patch by Tal Einat.
- bpo-16233: A module browser (File : Class Browser, Alt+C) requires an editor window with a filename. When Class Browser is requested otherwise, from a shell, output window, or ‘Untitled’ editor, Idle no longer displays an error box. It now pops up an Open Module box (Alt+M). If a valid name is entered and a module is opened, a corresponding browser is also opened.
- bpo-4832: Save As to type Python files automatically adds .py to the name you enter (even if your system does not display it). Some systems automatically add .txt when type is Text files.
- bpo-21986: Code objects are not normally pickled by the pickle module. To match this, they are no longer pickled when running under Idle.
- bpo-17390: Adjust Editor window title; remove ‘Python’, move version to end.
- bpo-14105: Idle debugger breakpoints no longer disappear when inserting or deleting lines.
- bpo-17172: Turtledemo can now be run from Idle. Currently, the entry is on the Help menu, but it may move to Run. Patch by Ramchandra Apt and Lita Cho.
- bpo-21765: Add support for non-ascii identifiers to HyperParser.
- bpo-21940: Add unittest for WidgetRedirector. Initial patch by Saimadhav Heblikar.
- bpo-18592: Add unittest for SearchDialogBase. Patch by Phil Webster.
- bpo-21694: Add unittest for ParenMatch. Patch by Saimadhav Heblikar.
- bpo-21686: add unittest for HyperParser. Original patch by Saimadhav Heblikar.
- bpo-12387: Add missing upper(lower)case versions of default Windows key bindings for Idle so Caps Lock does not disable them. Patch by Roger Serwy.
- bpo-21695: Closing a Find-in-files output window while the search is still in progress no longer closes Idle.
- bpo-18910: Add unittest for textView. Patch by Phil Webster.
- bpo-18292: Add unittest for AutoExpand. Patch by Saihadhav Heblikar.
- bpo-18409: Add unittest for AutoComplete. Patch by Phil Webster.
- bpo-21477: htest.py - Improve framework, complete set of tests. Patches by Saimadhav Heblikar
- bpo-18104: Add idlelib/idle_test/htest.py with a few sample tests to begin consolidating and improving human-validated tests of Idle. Change other files as needed to work with htest. Running the module as __main__ runs all tests.
- bpo-21139: Change default paragraph width to 72, the PEP 8 recommendation.
- bpo-21284: Paragraph reformat test passes after user changes reformat width.
- bpo-17654: Ensure IDLE menus are customized properly on OS X for non-framework builds and for all variants of Tk.
- bpo-23180: Rename IDLE “Windows” menu item to “Window”. Patch by Al Sweigart.

### Build

- bpo-15506: Use standard PKG_PROG_PKG_CONFIG autoconf macro in the configure script.
- bpo-22935: Allow the ssl module to be compiled if openssl doesn’t support SSL 3.
- bpo-22592: Drop support of the Borland C compiler to build Python. The distutils module still supports it to build extensions.
- bpo-22591: Drop support of MS-DOS, especially of the DJGPP compiler (MS-DOS port of GCC).
- bpo-16537: Check whether self.extensions is empty in setup.py. Patch by Jonathan Hosmer.
- bpo-22359: Remove incorrect uses of recursive make. Patch by Jonas Wagner.
- bpo-21958: Define HAVE_ROUND when building with Visual Studio 2013 and above. Patch by Zachary Turner.
- bpo-18093: the programs that embed the CPython runtime are now in a separate “Programs” directory, rather than being kept in the Modules directory.
- bpo-15759: “make suspicious”, “make linkcheck” and “make doctest” in Doc/ now display special message when and only when there are failures.
- bpo-21141: The Windows build process no longer attempts to find Perl, instead relying on OpenSSL source being configured and ready to build. The `PCbuild\build_ssl.py` script has been re-written and re-named to `PCbuild\prepare_ssl.py`, and takes care of configuring OpenSSL source for both 32 and 64 bit platforms. OpenSSL sources obtained from svn.python.org will always be pre-configured and ready to build.
- bpo-21037: Add a build option to enable AddressSanitizer support.
- bpo-19962: The Windows build process now creates “python.bat” in the root of the source tree, which passes all arguments through to the most recently built interpreter.
- bpo-21285: Refactor and fix curses configure check to always search in a ncursesw directory.
- bpo-15234: For BerkelyDB and Sqlite, only add the found library and include directories if they aren’t already being searched. This avoids an explicit runtime library dependency.
- bpo-17861: Tools/scripts/generate_opcode_h.py automatically regenerates Include/opcode.h from Lib/opcode.py if the latter gets any change.
- bpo-20644: OS X installer build support for documentation build changes in 3.4.1: assume externally supplied sphinx-build is available in /usr/bin.
- bpo-20022: Eliminate use of deprecated bundlebuilder in OS X builds.
- bpo-15968: Incorporated Tcl, Tk, and Tix builds into the Windows build solution.
- bpo-17095: Fix Modules/Setup shared support.
- bpo-21811: Anticipated fixes to support OS X versions > 10.9.
- bpo-21166: Prevent possible segfaults and other random failures of python –generate-posix-vars in pybuilddir.txt build target.
- bpo-18096: Fix library order returned by python-config.
- bpo-17219: Add library build dir for Python extension cross-builds.
- bpo-22919: Windows build updated to support VC 14.0 (Visual Studio 2015), which will be used for the official release.
- bpo-21236: Build _msi.pyd with cabinet.lib instead of fci.lib
- bpo-17128: Use private version of OpenSSL for OS X 10.5+ installer.

### C API

- bpo-14203: Remove obsolete support for view==NULL in PyBuffer_FillInfo(), bytearray_getbuffer(), bytesiobuf_getbuffer() and array_buffer_getbuf(). All functions now raise BufferError in that case.
- bpo-22445: PyBuffer_IsContiguous() now implements precise contiguity tests, compatible with NumPy’s NPY_RELAXED_STRIDES_CHECKING compilation flag. Previously the function reported false negatives for corner cases.
- bpo-22079: PyType_Ready() now checks that statically allocated type has no dynamically allocated bases.
- bpo-22453: Removed non-documented macro PyObject_REPR().
- bpo-18395: Rename `_Py_char2wchar()` to `Py_DecodeLocale()`, rename `_Py_wchar2char()` to `Py_EncodeLocale()`, and document these functions.
- bpo-21233: Add new C functions: PyMem_RawCalloc(), PyMem_Calloc(), PyObject_Calloc(), _PyObject_GC_Calloc(). bytes(int) is now using `calloc()` instead of `malloc()` for large objects which is faster and use less memory.
- bpo-20942: PyImport_ImportFrozenModuleObject() no longer sets __file__ to match what importlib does; this affects _frozen_importlib as well as any module loaded using imp.init_frozen().

### Documentation

- bpo-19548: Update the codecs module documentation to better cover the distinction between text encodings and other codecs, together with other clarifications. Patch by Martin Panter.
- bpo-22394: Doc/Makefile now supports `make venv PYTHON=../python` to create a venv for generating the documentation, e.g., `make html PYTHON=venv/bin/python3`.
- bpo-21514: The documentation of the json module now refers to new JSON RFC 7159 instead of obsoleted RFC 4627.
- bpo-21777: The binary sequence methods on bytes and bytearray are now documented explicitly, rather than assuming users will be able to derive the expected behaviour from the behaviour of the corresponding str methods.
- bpo-6916: undocument deprecated asynchat.fifo class.
- bpo-17386: Expanded functionality of the `Doc/make.bat` script to make it much more comparable to `Doc/Makefile`.
- bpo-21312: Update the thread_foobar.h template file to include newer threading APIs. Patch by Jack McCracken.
- bpo-21043: Remove the recommendation for specific CA organizations and to mention the ability to load the OS certificates.
- bpo-20765: Add missing documentation for PurePath.with_name() and PurePath.with_suffix().
- bpo-19407: New package installation and distribution guides based on the Python Packaging Authority tools. Existing guides have been retained as legacy links from the distutils docs, as they still contain some required reference material for tool developers that isn’t recorded anywhere else.
- bpo-19697: Document cases where __main__.__spec__ is None.

### Tests

- bpo-18982: Add tests for CLI of the calendar module.
- bpo-19548: Added some additional checks to test_codecs to ensure that statements in the updated documentation remain accurate. Patch by Martin Panter.
- bpo-22838: All test_re tests now work with unittest test discovery.
- bpo-22173: Update lib2to3 tests to use unittest test discovery.
- bpo-16000: Convert test_curses to use unittest.
- bpo-21456: Skip two tests in test_urllib2net.py if _ssl module not present. Patch by Remi Pointel.
- bpo-20746: Fix test_pdb to run in refleak mode (-R). Patch by Xavier de Gaye.
- bpo-22060: test_ctypes has been somewhat cleaned up and simplified; it now uses unittest test discovery to find its tests.
- bpo-22104: regrtest.py no longer holds a reference to the suite of tests loaded from test modules that don’t define test_main().
- bpo-22111: Assorted cleanups in test_imaplib. Patch by Milan Oberkirch.
- bpo-22002: Added `load_package_tests` function to test.support and used it to implement/augment test discovery in test_asyncio, test_email, test_importlib, test_json, and test_tools.
- bpo-21976: Fix test_ssl to accept LibreSSL version strings. Thanks to William Orr.
- bpo-21918: Converted test_tools from a module to a package containing separate test files for each tested script.
- bpo-9554: Use modern unittest features in test_argparse. Initial patch by Denver Coneybeare and Radu Voicilas.
- bpo-20155: Changed HTTP method names in failing tests in test_httpservers so that packet filtering software (specifically Windows Base Filtering Engine) does not interfere with the transaction semantics expected by the tests.
- bpo-19493: Refactored the ctypes test package to skip tests explicitly rather than silently.
- bpo-18492: All resources are now allowed when tests are not run by regrtest.py.
- bpo-21634: Fix pystone micro-benchmark: use floor division instead of true division to benchmark integers instead of floating point numbers. Set pystone version to 1.2. Patch written by Lennart Regebro.
- bpo-21605: Added tests for Tkinter images.
- bpo-21493: Added test for ntpath.expanduser(). Original patch by Claudiu Popa.
- bpo-19925: Added tests for the spwd module. Original patch by Vajrasky Kok.
- bpo-21522: Added Tkinter tests for Listbox.itemconfigure(), PanedWindow.paneconfigure(), and Menu.entryconfigure().
- bpo-17756: Fix test_code test when run from the installed location.
- bpo-17752: Fix distutils tests when run from the installed location.
- bpo-18604: Consolidated checks for GUI availability. All platforms now at least check whether Tk can be instantiated when the GUI resource is requested.
- bpo-21275: Fix a socket test on KFreeBSD.
- bpo-21223: Pass test_site/test_startup_imports when some of the extensions are built as builtins.
- bpo-20635: Added tests for Tk geometry managers.
- Add test case for freeze.
- bpo-20743: Fix a reference leak in test_tcl.
- bpo-21097: Move test_namespace_pkgs into test_importlib.
- bpo-21503: Use test_both() consistently in test_importlib.
- bpo-20939: Avoid various network test failures due to new redirect of http://www.python.org/ to https://www.python.org: use http://www.example.com instead.
- bpo-20668: asyncio tests no longer rely on tests.txt file. (Patch by Vajrasky Kok)
- bpo-21093: Prevent failures of ctypes test_macholib on OS X if a copy of libz exists in $HOME/lib or /usr/local/lib.
- bpo-22770: Prevent some Tk segfaults on OS X when running gui tests.
- bpo-23211: Workaround test_logging failure on some OS X 10.6 systems.
- bpo-23345: Prevent test_ssl failures with large OpenSSL patch level values (like 0.9.8zc).

### Tools/Demos

- bpo-22314: pydoc now works when the LINES environment variable is set.
- bpo-22615: Argument Clinic now supports the “type” argument for the int converter. This permits using the int converter with enums and typedefs.
- bpo-20076: The makelocalealias.py script no longer ignores UTF-8 mapping.
- bpo-20079: The makelocalealias.py script now can parse the SUPPORTED file from glibc sources and supports command line options for source paths.
- bpo-22201: Command-line interface of the zipfile module now correctly extracts ZIP files with directory entries. Patch by Ryan Wilson.
- bpo-22120: For functions using an unsigned integer return converter, Argument Clinic now generates a cast to that type for the comparison to -1 in the generated code. (This suppresses a compilation warning.)
- bpo-18974: Tools/scripts/diff.py now uses argparse instead of optparse.
- bpo-21906: Make Tools/scripts/md5sum.py work in Python 3. Patch by Zachary Ware.
- bpo-21629: Fix Argument Clinic’s “–converters” feature.
- Add support for `yield from` to 2to3.
- Add support for the PEP 465 matrix multiplication operator to 2to3.
- bpo-16047: Fix module exception list and __file__ handling in freeze. Patch by Meador Inge.
- bpo-11824: Consider ABI tags in freeze. Patch by Meador Inge.
- bpo-20535: PYTHONWARNING no longer affects the run_tests.py script. Patch by Arfrever Frehtes Taifersar Arahesis.

### Windows

- bpo-23260: Update Windows installer
- The bundled version of Tcl/Tk has been updated to 8.6.3. The most visible result of this change is the addition of new native file dialogs when running on Windows Vista or newer. See Tcl/Tk’s TIP 432 for more information. Also, this version of Tcl/Tk includes support for Windows 10.
- bpo-17896: The Windows build scripts now expect external library sources to be in `PCbuild\..\externals` rather than `PCbuild\..\..`.
- bpo-17717: The Windows build scripts now use a copy of NASM pulled from svn.python.org to build OpenSSL.
- bpo-21907: Improved the batch scripts provided for building Python.
- bpo-22644: The bundled version of OpenSSL has been updated to 1.0.1j.
- bpo-10747: Use versioned labels in the Windows start menu. Patch by Olive Kilburn.
- bpo-22980: .pyd files with a version and platform tag (for example, “.cp35-win32.pyd”) will now be loaded in preference to those without tags.

(For information about older versions, consult the HISTORY file.)