cpython/Doc/c-api/list.rst

.. highlightlang:: c

.. _listobjects:

List Objects
------------

.. index:: object: list


.. c:type:: PyListObject

   This subtype of :c:type:`PyObject` represents a Python list object.


.. c:var:: PyTypeObject PyList_Type

   This instance of :c:type:`PyTypeObject` represents the Python list type.
   This is the same object as :class:`list` in the Python layer.


.. c:function:: int PyList_Check(PyObject *p)

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


.. c:function:: int PyList_CheckExact(PyObject *p)

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


.. c:function:: PyObject* PyList_New(Py_ssize_t len)

   Return a new list of length *len* on success, or *NULL* on failure.

   .. note::

      If *len* is greater than zero, the returned list object's items are
      set to ``NULL``.  Thus you cannot use abstract API functions such as
      :c:func:`PySequence_SetItem`  or expose the object to Python code before
      setting all items to a real object with :c:func:`PyList_SetItem`.


.. c:function:: Py_ssize_t PyList_Size(PyObject *list)

   .. index:: builtin: len

   Return the length of the list object in *list*; this is equivalent to
   ``len(list)`` on a list object.


.. c:function:: Py_ssize_t PyList_GET_SIZE(PyObject *list)

   Macro form of :c:func:`PyList_Size` without error checking.


.. c:function:: PyObject* PyList_GetItem(PyObject *list, Py_ssize_t index)

   Return the object at position *index* in the list pointed to by *list*.  The
   position must be positive, indexing from the end of the list is not
   supported.  If *index* is out of bounds, return *NULL* and set an
   :exc:`IndexError` exception.


.. c:function:: PyObject* PyList_GET_ITEM(PyObject *list, Py_ssize_t i)

   Macro form of :c:func:`PyList_GetItem` without error checking.


.. c:function:: int PyList_SetItem(PyObject *list, Py_ssize_t index, PyObject *item)

   Set the item at index *index* in list to *item*.  Return ``0`` on success
   or ``-1`` on failure.

   .. note::

      This function "steals" a reference to *item* and discards a reference to
      an item already in the list at the affected position.


.. c:function:: void PyList_SET_ITEM(PyObject *list, Py_ssize_t i, PyObject *o)

   Macro form of :c:func:`PyList_SetItem` without error checking. This is
   normally only used to fill in new lists where there is no previous content.

   .. note::

      This macro "steals" a reference to *item*, and, unlike
      :c:func:`PyList_SetItem`, does *not* discard a reference to any item that
      is being replaced; any reference in *list* at position *i* will be
      leaked.


.. c:function:: int PyList_Insert(PyObject *list, Py_ssize_t index, PyObject *item)

   Insert the item *item* into list *list* in front of index *index*.  Return
   ``0`` if successful; return ``-1`` and set an exception if unsuccessful.
   Analogous to ``list.insert(index, item)``.


.. c:function:: int PyList_Append(PyObject *list, PyObject *item)

   Append the object *item* at the end of list *list*. Return ``0`` if
   successful; return ``-1`` and set an exception if unsuccessful.  Analogous
   to ``list.append(item)``.


.. c:function:: PyObject* PyList_GetSlice(PyObject *list, Py_ssize_t low, Py_ssize_t high)

   Return a list of the objects in *list* containing the objects *between* *low*
   and *high*.  Return *NULL* and set an exception if unsuccessful.  Analogous
   to ``list[low:high]``.  Negative indices, as when slicing from Python, are not
   supported.


.. c:function:: int PyList_SetSlice(PyObject *list, Py_ssize_t low, Py_ssize_t high, PyObject *itemlist)

   Set the slice of *list* between *low* and *high* to the contents of
   *itemlist*.  Analogous to ``list[low:high] = itemlist``. The *itemlist* may
   be *NULL*, indicating the assignment of an empty list (slice deletion).
   Return ``0`` on success, ``-1`` on failure.  Negative indices, as when
   slicing from Python, are not supported.


.. c:function:: int PyList_Sort(PyObject *list)

   Sort the items of *list* in place.  Return ``0`` on success, ``-1`` on
   failure.  This is equivalent to ``list.sort()``.


.. c:function:: int PyList_Reverse(PyObject *list)

   Reverse the items of *list* in place.  Return ``0`` on success, ``-1`` on
   failure.  This is the equivalent of ``list.reverse()``.


.. c:function:: PyObject* PyList_AsTuple(PyObject *list)

   .. index:: builtin: tuple

   Return a new tuple object containing the contents of *list*; equivalent to
   ``tuple(list)``.


.. c:function:: int PyList_ClearFreeList()

   Clear the free list. Return the total number of freed items.

   .. versionadded:: 3.3