mirror of https://github.com/python/cpython
247 lines
8.1 KiB
ReStructuredText
247 lines
8.1 KiB
ReStructuredText
.. highlight:: c
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.. _tupleobjects:
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Tuple Objects
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-------------
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.. index:: pair: object; tuple
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.. c:type:: PyTupleObject
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This subtype of :c:type:`PyObject` represents a Python tuple object.
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.. c:var:: PyTypeObject PyTuple_Type
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This instance of :c:type:`PyTypeObject` represents the Python tuple type; it
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is the same object as :class:`tuple` in the Python layer.
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.. c:function:: int PyTuple_Check(PyObject *p)
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Return true if *p* is a tuple object or an instance of a subtype of the
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tuple type. This function always succeeds.
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.. c:function:: int PyTuple_CheckExact(PyObject *p)
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Return true if *p* is a tuple object, but not an instance of a subtype of the
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tuple type. This function always succeeds.
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.. c:function:: PyObject* PyTuple_New(Py_ssize_t len)
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Return a new tuple object of size *len*, or ``NULL`` on failure.
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.. c:function:: PyObject* PyTuple_Pack(Py_ssize_t n, ...)
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Return a new tuple object of size *n*, or ``NULL`` on failure. The tuple values
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are initialized to the subsequent *n* C arguments pointing to Python objects.
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``PyTuple_Pack(2, a, b)`` is equivalent to ``Py_BuildValue("(OO)", a, b)``.
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.. c:function:: Py_ssize_t PyTuple_Size(PyObject *p)
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Take a pointer to a tuple object, and return the size of that tuple.
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.. c:function:: Py_ssize_t PyTuple_GET_SIZE(PyObject *p)
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Return the size of the tuple *p*, which must be non-``NULL`` and point to a tuple;
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no error checking is performed.
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.. c:function:: PyObject* PyTuple_GetItem(PyObject *p, Py_ssize_t pos)
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Return the object at position *pos* in the tuple pointed to by *p*. If *pos* is
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negative or out of bounds, return ``NULL`` and set an :exc:`IndexError` exception.
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The returned reference is borrowed from the tuple *p*
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(that is: it is only valid as long as you hold a reference to *p*).
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To get a :term:`strong reference`, use
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:c:func:`Py_NewRef(PyTuple_GetItem(...)) <Py_NewRef>`
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or :c:func:`PySequence_GetItem`.
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.. c:function:: PyObject* PyTuple_GET_ITEM(PyObject *p, Py_ssize_t pos)
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Like :c:func:`PyTuple_GetItem`, but does no checking of its arguments.
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.. c:function:: PyObject* PyTuple_GetSlice(PyObject *p, Py_ssize_t low, Py_ssize_t high)
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Return the slice of the tuple pointed to by *p* between *low* and *high*,
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or ``NULL`` on failure. This is the equivalent of the Python expression
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``p[low:high]``. Indexing from the end of the tuple is not supported.
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.. c:function:: int PyTuple_SetItem(PyObject *p, Py_ssize_t pos, PyObject *o)
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Insert a reference to object *o* at position *pos* of the tuple pointed to by
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*p*. Return ``0`` on success. If *pos* is out of bounds, return ``-1``
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and set an :exc:`IndexError` exception.
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.. note::
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This function "steals" a reference to *o* and discards a reference to
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an item already in the tuple at the affected position.
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.. c:function:: void PyTuple_SET_ITEM(PyObject *p, Py_ssize_t pos, PyObject *o)
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Like :c:func:`PyTuple_SetItem`, but does no error checking, and should *only* be
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used to fill in brand new tuples.
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Bounds checking is performed as an assertion if Python is built in
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:ref:`debug mode <debug-build>` or :option:`with assertions <--with-assertions>`.
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.. note::
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This function "steals" a reference to *o*, and, unlike
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:c:func:`PyTuple_SetItem`, does *not* discard a reference to any item that
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is being replaced; any reference in the tuple at position *pos* will be
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leaked.
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.. warning::
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This macro should *only* be used on tuples that are newly created.
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Using this macro on a tuple that is already in use (or in other words, has
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a refcount > 1) could lead to undefined behavior.
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.. c:function:: int _PyTuple_Resize(PyObject **p, Py_ssize_t newsize)
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Can be used to resize a tuple. *newsize* will be the new length of the tuple.
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Because tuples are *supposed* to be immutable, this should only be used if there
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is only one reference to the object. Do *not* use this if the tuple may already
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be known to some other part of the code. The tuple will always grow or shrink
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at the end. Think of this as destroying the old tuple and creating a new one,
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only more efficiently. Returns ``0`` on success. Client code should never
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assume that the resulting value of ``*p`` will be the same as before calling
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this function. If the object referenced by ``*p`` is replaced, the original
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``*p`` is destroyed. On failure, returns ``-1`` and sets ``*p`` to ``NULL``, and
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raises :exc:`MemoryError` or :exc:`SystemError`.
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.. _struct-sequence-objects:
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Struct Sequence Objects
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-----------------------
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Struct sequence objects are the C equivalent of :func:`~collections.namedtuple`
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objects, i.e. a sequence whose items can also be accessed through attributes.
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To create a struct sequence, you first have to create a specific struct sequence
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type.
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.. c:function:: PyTypeObject* PyStructSequence_NewType(PyStructSequence_Desc *desc)
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Create a new struct sequence type from the data in *desc*, described below. Instances
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of the resulting type can be created with :c:func:`PyStructSequence_New`.
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.. c:function:: void PyStructSequence_InitType(PyTypeObject *type, PyStructSequence_Desc *desc)
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Initializes a struct sequence type *type* from *desc* in place.
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.. c:function:: int PyStructSequence_InitType2(PyTypeObject *type, PyStructSequence_Desc *desc)
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The same as ``PyStructSequence_InitType``, but returns ``0`` on success and ``-1`` on
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failure.
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.. versionadded:: 3.4
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.. c:type:: PyStructSequence_Desc
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Contains the meta information of a struct sequence type to create.
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.. c:member:: const char *name
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Name of the struct sequence type.
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.. c:member:: const char *doc
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Pointer to docstring for the type or ``NULL`` to omit.
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.. c:member:: PyStructSequence_Field *fields
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Pointer to ``NULL``-terminated array with field names of the new type.
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.. c:member:: int n_in_sequence
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Number of fields visible to the Python side (if used as tuple).
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.. c:type:: PyStructSequence_Field
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Describes a field of a struct sequence. As a struct sequence is modeled as a
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tuple, all fields are typed as :c:expr:`PyObject*`. The index in the
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:c:member:`~PyStructSequence_Desc.fields` array of
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the :c:type:`PyStructSequence_Desc` determines which
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field of the struct sequence is described.
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.. c:member:: const char *name
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Name for the field or ``NULL`` to end the list of named fields,
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set to :c:data:`PyStructSequence_UnnamedField` to leave unnamed.
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.. c:member:: const char *doc
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Field docstring or ``NULL`` to omit.
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.. c:var:: const char * const PyStructSequence_UnnamedField
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Special value for a field name to leave it unnamed.
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.. versionchanged:: 3.9
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The type was changed from ``char *``.
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.. c:function:: PyObject* PyStructSequence_New(PyTypeObject *type)
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Creates an instance of *type*, which must have been created with
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:c:func:`PyStructSequence_NewType`.
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.. c:function:: PyObject* PyStructSequence_GetItem(PyObject *p, Py_ssize_t pos)
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Return the object at position *pos* in the struct sequence pointed to by *p*.
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Bounds checking is performed as an assertion if Python is built in
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:ref:`debug mode <debug-build>` or :option:`with assertions <--with-assertions>`.
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.. c:function:: PyObject* PyStructSequence_GET_ITEM(PyObject *p, Py_ssize_t pos)
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Alias to :c:func:`PyStructSequence_GetItem`.
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.. versionchanged:: 3.13
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Now implemented as an alias to :c:func:`PyStructSequence_GetItem`.
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.. c:function:: void PyStructSequence_SetItem(PyObject *p, Py_ssize_t pos, PyObject *o)
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Sets the field at index *pos* of the struct sequence *p* to value *o*. Like
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:c:func:`PyTuple_SET_ITEM`, this should only be used to fill in brand new
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instances.
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Bounds checking is performed as an assertion if Python is built in
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:ref:`debug mode <debug-build>` or :option:`with assertions <--with-assertions>`.
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.. note::
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This function "steals" a reference to *o*.
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.. c:function:: void PyStructSequence_SET_ITEM(PyObject *p, Py_ssize_t *pos, PyObject *o)
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Alias to :c:func:`PyStructSequence_SetItem`.
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.. versionchanged:: 3.13
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Now implemented as an alias to :c:func:`PyStructSequence_SetItem`.
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