Tuple Objects — Python 3.9.1 documentation

# Tuple Objects

`PyTupleObject`

  This subtype of `PyObject` represents a Python tuple object.

PyTypeObject `PyTuple_Type`

  This instance of `PyTypeObject` represents the Python tuple type; it is the same object as `tuple` in the Python layer.

int `PyTuple_Check`(PyObject *p)

  Return true if p is a tuple object or an instance of a subtype of the tuple type.

int `PyTuple_CheckExact`(PyObject *p)

  Return true if p is a tuple object, but not an instance of a subtype of the tuple type.

PyObject* `PyTuple_New`(Py_ssize_t len)
  Return value: New reference.

  Return a new tuple object of size len, or `NULL` on failure.

PyObject* `PyTuple_Pack`(Py_ssize_t n, ...)
  Return value: New reference.

  Return a new tuple object of size n, or `NULL` on failure. The tuple values are initialized to the subsequent n C arguments pointing to Python objects. `PyTuple_Pack(2, a, b)` is equivalent to `Py_BuildValue("(OO)", a, b)`.

Py_ssize_t `PyTuple_Size`(PyObject *p)

  Take a pointer to a tuple object, and return the size of that tuple.

Py_ssize_t `PyTuple_GET_SIZE`(PyObject *p)

  Return the size of the tuple p, which must be non-`NULL` and point to a tuple; no error checking is performed.

PyObject* `PyTuple_GetItem`(PyObject *p, Py_ssize_t pos)
  Return value: Borrowed reference.

  Return the object at position pos in the tuple pointed to by p. If pos is out of bounds, return `NULL` and set an `IndexError` exception.

PyObject* `PyTuple_GET_ITEM`(PyObject *p, Py_ssize_t pos)
  Return value: Borrowed reference.

  Like `PyTuple_GetItem()`, but does no checking of its arguments.

PyObject* `PyTuple_GetSlice`(PyObject *p, Py_ssize_t low, Py_ssize_t high)
  Return value: New reference.

  Return the slice of the tuple pointed to by p between low and high, or `NULL` on failure. This is the equivalent of the Python expression `p[low:high]`. Indexing from the end of the list is not supported.

int `PyTuple_SetItem`(PyObject *p, Py_ssize_t pos, PyObject *o)

  Insert a reference to object o at position pos of the tuple pointed to by p. Return `0` on success. If pos is out of bounds, return `-1` and set an `IndexError` exception.

  Note

  This function “steals” a reference to o and discards a reference to an item already in the tuple at the affected position.

void `PyTuple_SET_ITEM`(PyObject *p, Py_ssize_t pos, PyObject *o)

  Like `PyTuple_SetItem()`, but does no error checking, and should only be used to fill in brand new tuples.

  Note

  This macro “steals” a reference to o, and, unlike `PyTuple_SetItem()`, does not discard a reference to any item that is being replaced; any reference in the tuple at position pos will be leaked.

int `_PyTuple_Resize`(PyObject **p, Py_ssize_t newsize)

  Can be used to resize a tuple. newsize will be the new length of the tuple. Because tuples are supposed to be immutable, this should only be used if there is only one reference to the object. Do not use this if the tuple may already be known to some other part of the code. The tuple will always grow or shrink at the end. Think of this as destroying the old tuple and creating a new one, only more efficiently. Returns `0` on success. Client code should never assume that the resulting value of `*p` will be the same as before calling this function. If the object referenced by `*p` is replaced, the original `*p` is destroyed. On failure, returns `-1` and sets `*p` to `NULL`, and raises `MemoryError` or `SystemError`.

# Struct Sequence Objects

Struct sequence objects are the C equivalent of `namedtuple()` objects, i.e. a sequence whose items can also be accessed through attributes. To create a struct sequence, you first have to create a specific struct sequence type.

PyTypeObject* `PyStructSequence_NewType`(PyStructSequence_Desc *desc)
  Return value: New reference.

  Create a new struct sequence type from the data in desc, described below. Instances of the resulting type can be created with `PyStructSequence_New()`.

void `PyStructSequence_InitType`(PyTypeObject *type, PyStructSequence_Desc *desc)

  Initializes a struct sequence type type from desc in place.

int `PyStructSequence_InitType2`(PyTypeObject *type, PyStructSequence_Desc *desc)

  The same as `PyStructSequence_InitType`, but returns `0` on success and `-1` on failure.

  New in version 3.4.

`PyStructSequence_Desc`

  Contains the meta information of a struct sequence type to create.

  Field | C Type | Meaning
  --- | --- | ---
  `name` | `const char *` | name of the struct sequence type
  `doc` | `const char *` | pointer to docstring for the type or `NULL` to omit
  `fields` | `PyStructSequence_Field *` | pointer to `NULL`-terminated array with field names of the new type
  `n_in_sequence` | `int` | number of fields visible to the Python side (if used as tuple)

`PyStructSequence_Field`

  Describes a field of a struct sequence. As a struct sequence is modeled as a tuple, all fields are typed as `PyObject*`. The index in the `fields` array of the `PyStructSequence_Desc` determines which field of the struct sequence is described.

  Field | C Type | Meaning
  --- | --- | ---
  `name` | `const char *` | name for the field or `NULL` to end the list of named fields, set to `PyStructSequence_UnnamedField` to leave unnamed
  `doc` | `const char *` | field docstring or `NULL` to omit

const char * const `PyStructSequence_UnnamedField`

  Special value for a field name to leave it unnamed.

  Changed in version 3.9: The type was changed from `char *`.

PyObject* `PyStructSequence_New`(PyTypeObject *type)
  Return value: New reference.

  Creates an instance of type, which must have been created with `PyStructSequence_NewType()`.

PyObject* `PyStructSequence_GetItem`(PyObject *p, Py_ssize_t pos)
  Return value: Borrowed reference.

  Return the object at position pos in the struct sequence pointed to by p. No bounds checking is performed.

PyObject* `PyStructSequence_GET_ITEM`(PyObject *p, Py_ssize_t pos)
  Return value: Borrowed reference.

  Macro equivalent of `PyStructSequence_GetItem()`.

void `PyStructSequence_SetItem`(PyObject *p, Py_ssize_t pos, PyObject *o)

  Sets the field at index pos of the struct sequence p to value o. Like `PyTuple_SET_ITEM()`, this should only be used to fill in brand new instances.

  Note

  This function “steals” a reference to o.

void `PyStructSequence_SET_ITEM`(PyObject *p, Py_ssize_t *pos, PyObject *o)

  Macro equivalent of `PyStructSequence_SetItem()`.

  Note

  This function “steals” a reference to o.