PyMemoryView (Jython API documentation)
Date: 2022-09-10

org.python.core

## Class PyMemoryView

- java.lang.Object
- - org.python.core.PyObject
  - - org.python.core.PySequence
    - - org.python.core.PyMemoryView

- All Implemented Interfaces:
    java.io.Serializable, BufferProtocol, Traverseproc

      public class PyMemoryView
      extends PySequence
      implements BufferProtocol, Traverseproc

  Class implementing the Python `memoryview` type. It provides a wrapper around the Jython buffer API.
  See Also:
    Serialized Form

- - ### Nested Class Summary

    - ### Nested classes/interfaces inherited from class org.python.core.PyObject

      `PyObject.ConversionException`

  - ### Field Summary

    Fields
    Modifier and Type | Field and Description
    --- | ---
    `static PyType` | `TYPE`

    - ### Fields inherited from class org.python.core.PyObject

      `gcMonitorGlobal`

  - ### Constructor Summary

    Constructors
    Constructor and Description
    `PyMemoryView(BufferProtocol pybuf)` Construct a `PyMemoryView` from an object bearing the `BufferProtocol` interface.

  - ### Method Summary

    All Methods Instance Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `PyObject` | `__enter__()` Called at the start of a context-managed suite (supporting the `with` clause).
    `PyObject` | `__eq__(PyObject other)` Equivalent to the standard Python __eq__ method.
    `boolean` | `__exit__(PyObject type, PyObject value, PyObject traceback)` Called at the end of a context-managed suite (supporting the `with` clause), and will release the `memoryview`.
    `PyObject` | `__ge__(PyObject other)` Equivalent to the standard Python __ge__ method.
    `PyObject` | `__gt__(PyObject other)` Equivalent to the standard Python __gt__ method.
    `PyObject` | `__le__(PyObject other)` Equivalent to the standard Python __le__ method.
    `int` | `__len__()` Equivalent to the standard Python __len__ method.
    `PyObject` | `__lt__(PyObject other)` Equivalent to the standard Python __lt__ method.
    `PyObject` | `__ne__(PyObject other)` Equivalent to the standard Python __ne__ method.
    `java.lang.Object` | `__tojava__(java.lang.Class<?> c)` Equivalent to the Jython __tojava__ method.
    `java.lang.String` | `format()`
    `PyBuffer` | `getBuffer(int flags)` Method by which the consumer requests the buffer from the exporter.
    `int` | `hashCode()`
    `int` | `itemsize()`
    `void` | `memoryview_release()`
    `int` | `ndim()`
    `PyObject` | `obj()`
    `void` | `pyset(int index, PyObject value)` Sets the indexed element of the memoryview to the given value, treating the operation as assignment to a slice of length one.
    `boolean` | `readonly()`
    `boolean` | `refersDirectlyTo(PyObject ob)` Optional operation.
    `void` | `release()` Request a release of the underlying buffer exposed by the `memoryview` object.
    `PyObject` | `shape()`
    `PyObject` | `strides()`
    `PyObject` | `suboffsets()`
    `PyString` | `tobytes()` Implementation of Python `tobytes()`.
    `PyList` | `tolist()` Implementation of Python `tolist()`.
    `int` | `traverse(Visitproc visit, java.lang.Object arg)` Traverses all directly contained `PyObject`s.

    - ### Methods inherited from class org.python.core.PySequence

      `__delitem__, __delslice__, __finditem__, __finditem__, __getitem__, __getslice__, __iter__, __nonzero__, __setitem__, __setitem__, __setslice__, isMappingType, isNumberType, isSequenceType`

    - ### Methods inherited from class org.python.core.PyObject

      `__abs__, __add__, __and__, __call__, __call__, __call__, __call__, __call__, __call__, __call__, __call__, __call__, __call__, __call__, __call__, __call__, __call__, __call__, __call__, __cmp__, __coerce__, __coerce_ex__, __complex__, __contains__, __delattr__, __delattr__, __delete__, __delitem__, __delslice__, __dir__, __div__, __divmod__, __ensure_finalizer__, __findattr__, __findattr__, __findattr_ex__, __finditem__, __float__, __floordiv__, __format__, __get__, __getattr__, __getattr__, __getitem__, __getnewargs__, __getslice__, __hash__, __hex__, __iadd__, __iand__, __idiv__, __idivmod__, __ifloordiv__, __ilshift__, __imod__, __imul__, __index__, __int__, __invert__, __ior__, __ipow__, __irshift__, __isub__, __iternext__, __itruediv__, __ixor__, __long__, __lshift__, __mod__, __mul__, __neg__, __not__, __oct__, __or__, __pos__, __pow__, __pow__, __radd__, __rand__, __rdiv__, __rdivmod__, __reduce__, __reduce_ex__, __reduce_ex__, __repr__, __rfloordiv__, __rlshift__, __rmod__, __rmul__, __ror__, __rpow__, __rrshift__, __rshift__, __rsub__, __rtruediv__, __rxor__, __set__, __setattr__, __setattr__, __setitem__, __setslice__, __str__, __sub__, __truediv__, __trunc__, __unicode__, __xor__, _add, _and, _callextra, _cmp, _div, _divmod, _doget, _doget, _doset, _eq, _floordiv, _ge, _gt, _iadd, _iand, _idiv, _idivmod, _ifloordiv, _ilshift, _imod, _imul, _in, _ior, _ipow, _irshift, _is, _isnot, _isub, _itruediv, _ixor, _jcall, _jcallexc, _jthrow, _le, _lshift, _lt, _mod, _mul, _ne, _notin, _or, _pow, _rshift, _sub, _truediv, _xor, asDouble, asIndex, asIndex, asInt, asInt, asIterable, asLong, asLong, asName, asName, asString, asString, asStringOrNull, asStringOrNull, bit_length, conjugate, delDict, delType, dispatch__init__, equals, fastGetClass, fastGetDict, getDict, getType, implementsDescrDelete, implementsDescrGet, implementsDescrSet, invoke, invoke, invoke, invoke, invoke, invoke, isCallable, isDataDescr, isIndex, isInteger, noAttributeError, object___subclasshook__, readonlyAttributeError, setDict, setType, toString`

    - ### Methods inherited from class java.lang.Object

      `getClass, notify, notifyAll, wait, wait, wait`

- - ### Field Detail

    - #### TYPE

          public static final PyType TYPE

  - ### Constructor Detail

    - #### PyMemoryView

          public PyMemoryView(BufferProtocol pybuf)
                       throws java.lang.ClassCastException

      Construct a `PyMemoryView` from an object bearing the `BufferProtocol` interface. If this object is already an exported buffer, the `memoryview` takes a new lease on it. The buffer so obtained will be writable if the underlying object permits it.
      Parameters:
        `pybuf` - buffer exported by some underlying object
      Throws:
        `java.lang.ClassCastException` - in cases where `pybuf.getBuffer` does so.

  - ### Method Detail

    - #### __tojava__

          public java.lang.Object __tojava__(java.lang.Class<?> c)

      Description copied from class: `PyObject`
      Equivalent to the Jython __tojava__ method. Tries to coerce this object to an instance of the requested Java class. Returns the special object `Py.NoConversion` if this `PyObject` can not be converted to the desired Java class.
      Overrides:
        `__tojava__` in class `PySequence`
      Parameters:
        `c` - the Class to convert this `PyObject` to.

    - #### obj

          public PyObject obj()

    - #### format

          public java.lang.String format()

    - #### itemsize

          public int itemsize()

    - #### shape

          public PyObject shape()

    - #### ndim

          public int ndim()

    - #### strides

          public PyObject strides()

    - #### suboffsets

          public PyObject suboffsets()

    - #### readonly

          public boolean readonly()

    - #### tobytes

          public PyString tobytes()

      Implementation of Python `tobytes()`. Return the data in the buffer as a byte string (an object of class `str`).
      Returns:
        byte string of buffer contents.

    - #### tolist

          public PyList tolist()

      Implementation of Python `tolist()`. Return the data in the buffer as a `list` where the elements are an appropriate type (`int` in the case of a byte-oriented buffer, which is the only case presently supported).
      Returns:
        a list of buffer contents.

    - #### __len__

          public int __len__()

      Description copied from class: `PyObject`
      Equivalent to the standard Python __len__ method. Part of the mapping discipline.
      Overrides:
        `__len__` in class `PyObject`
      Returns:
        the length of the object

    - #### hashCode

          public int hashCode()

      Overrides:
        `hashCode` in class `PyObject`

    - #### __eq__

          public PyObject __eq__(PyObject other)

      Description copied from class: `PyObject`
      Equivalent to the standard Python __eq__ method.
      Overrides:
        `__eq__` in class `PySequence`
      Parameters:
        `other` - the object to compare this with.
      Returns:
        the result of the comparison.

    - #### __ne__

          public PyObject __ne__(PyObject other)

      Description copied from class: `PyObject`
      Equivalent to the standard Python __ne__ method.
      Overrides:
        `__ne__` in class `PySequence`
      Parameters:
        `other` - the object to compare this with.
      Returns:
        the result of the comparison.

    - #### __lt__

          public PyObject __lt__(PyObject other)

      Description copied from class: `PyObject`
      Equivalent to the standard Python __lt__ method.
      Overrides:
        `__lt__` in class `PySequence`
      Parameters:
        `other` - the object to compare this with.
      Returns:
        the result of the comparison.

    - #### __le__

          public PyObject __le__(PyObject other)

      Description copied from class: `PyObject`
      Equivalent to the standard Python __le__ method.
      Overrides:
        `__le__` in class `PySequence`
      Parameters:
        `other` - the object to compare this with.
      Returns:
        the result of the comparison.

    - #### __ge__

          public PyObject __ge__(PyObject other)

      Description copied from class: `PyObject`
      Equivalent to the standard Python __ge__ method.
      Overrides:
        `__ge__` in class `PySequence`
      Parameters:
        `other` - the object to compare this with.
      Returns:
        the result of the comparison.

    - #### __gt__

          public PyObject __gt__(PyObject other)

      Description copied from class: `PyObject`
      Equivalent to the standard Python __gt__ method.
      Overrides:
        `__gt__` in class `PySequence`
      Parameters:
        `other` - the object to compare this with.
      Returns:
        the result of the comparison.

    - #### __enter__

          public PyObject __enter__()

      Called at the start of a context-managed suite (supporting the `with` clause).
      Returns:
        this object

    - #### __exit__

          public boolean __exit__(PyObject type,
                                  PyObject value,
                                  PyObject traceback)

      Called at the end of a context-managed suite (supporting the `with` clause), and will release the `memoryview`.
      Returns:
        false

    - #### getBuffer

          public PyBuffer getBuffer(int flags)

      Method by which the consumer requests the buffer from the exporter. The consumer provides information on its ability to understand buffer navigation. Each consumer requesting a buffer in this way, when it has finished using it, should make a corresponding call to `PyBuffer.release()` on the buffer it obtained, or `PyBuffer.close()` using try-with-resources, since some objects alter their behaviour while buffers are exported.

      The `PyBuffer` returned from this method is just the one on which the `memoryview` was first constructed. The Jython buffer API is such that sharing directly is safe (as long as the get-release discipline is observed).

      Specified by:
        `getBuffer` in interface `BufferProtocol`
      Parameters:
        `flags` - specifying features demanded and the navigational capabilities of the consumer
      Returns:
        exported buffer

    - #### release

          public void release()

      Request a release of the underlying buffer exposed by the `memoryview` object. Many objects take special actions when a view is held on them (for example, a `bytearray` would temporarily forbid resizing); therefore, calling `release()` is handy to remove these restrictions (and free any dangling resources) as soon as possible.

      After this method has been called, any further operation on the view raises a `ValueError` (except `release()` itself which can be called multiple times with the same effect as just one call).

      This becomes an exposed method in CPython from 3.2. The Jython implementation of `memoryview` follows the Python 3.3 design internally and therefore safely anticipates Python 3 in exposing `memoryview.release` along with the related context-management behaviour.

    - #### memoryview_release

          public final void memoryview_release()

    - #### pyset

          public void pyset(int index,
                            PyObject value)
                     throws PyException

      Sets the indexed element of the memoryview to the given value, treating the operation as assignment to a slice of length one. This is different from the same operation on a byte array, where the assigned value must be an int: here it must have the buffer API and length one. This is an extension point called by PySequence in its implementation of `PySequence.__setitem__(int, org.python.core.PyObject)` It is guaranteed by PySequence that the index is within the bounds of the memoryview. Any other clients calling `pyset(int, PyObject)` must make the same guarantee.
      Parameters:
        `index` - index of the element to set.
        `value` - to set this element to, regarded as a buffer of length one unit.
      Throws:
        `PyException` - `AttributeError` if value cannot be converted to an integer
        `PyException` - `ValueError` if value<0 or value>255

    - #### traverse

          public int traverse(Visitproc visit,
                              java.lang.Object arg)

      Description copied from interface: `Traverseproc`
      Traverses all directly contained `PyObject`s. Like in CPython, `arg` must be passed unmodified to `visit` as its second parameter. If `Visitproc.visit(PyObject, Object)` returns nonzero, this return value must be returned immediately by traverse. `Visitproc.visit(PyObject, Object)` must not be called with a `null` PyObject-argument.
      Specified by:
        `traverse` in interface `Traverseproc`

    - #### refersDirectlyTo

          public boolean refersDirectlyTo(PyObject ob)

      Description copied from interface: `Traverseproc`
      Optional operation. Should only be implemented if it is more efficient than calling `Traverseproc.traverse(Visitproc, Object)` with a visitproc that just watches out for `ob`. Must return `false` if `ob` is `null`.
      Specified by:
        `refersDirectlyTo` in interface `Traverseproc`

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