source: python/trunk/Doc/c-api/slice.rst

.. highlightlang:: c

.. _slice-objects:

Slice Objects
-------------


.. c:var:: PyTypeObject PySlice_Type

   .. index:: single: SliceType (in module types)

   The type object for slice objects.  This is the same as ``slice`` and
   ``types.SliceType``.


.. c:function:: int PySlice_Check(PyObject *ob)

   Return true if *ob* is a slice object; *ob* must not be *NULL*.


.. c:function:: PyObject* PySlice_New(PyObject *start, PyObject *stop, PyObject *step)

   Return a new slice object with the given values.  The *start*, *stop*, and
   *step* parameters are used as the values of the slice object attributes of
   the same names.  Any of the values may be *NULL*, in which case the
   ``None`` will be used for the corresponding attribute.  Return *NULL* if
   the new object could not be allocated.


.. c:function:: int PySlice_GetIndices(PySliceObject *slice, Py_ssize_t length, Py_ssize_t *start, Py_ssize_t *stop, Py_ssize_t *step)

   Retrieve the start, stop and step indices from the slice object *slice*,
   assuming a sequence of length *length*. Treats indices greater than
   *length* as errors.

   Returns 0 on success and -1 on error with no exception set (unless one of
   the indices was not :const:`None` and failed to be converted to an integer,
   in which case -1 is returned with an exception set).

   You probably do not want to use this function.  If you want to use slice
   objects in versions of Python prior to 2.3, you would probably do well to
   incorporate the source of :c:func:`PySlice_GetIndicesEx`, suitably renamed,
   in the source of your extension.

   .. versionchanged:: 2.5
      This function used an :c:type:`int` type for *length* and an
      :c:type:`int *` type for *start*, *stop*, and *step*. This might require
      changes in your code for properly supporting 64-bit systems.


.. c:function:: int PySlice_GetIndicesEx(PySliceObject *slice, Py_ssize_t length, Py_ssize_t *start, Py_ssize_t *stop, Py_ssize_t *step, Py_ssize_t *slicelength)

   Usable replacement for :c:func:`PySlice_GetIndices`.  Retrieve the start,
   stop, and step indices from the slice object *slice* assuming a sequence of
   length *length*, and store the length of the slice in *slicelength*.  Out
   of bounds indices are clipped in a manner consistent with the handling of
   normal slices.

   Returns 0 on success and -1 on error with exception set.

   .. versionadded:: 2.3

   .. versionchanged:: 2.5
      This function used an :c:type:`int` type for *length* and an
      :c:type:`int *` type for *start*, *stop*, *step*, and *slicelength*. This
      might require changes in your code for properly supporting 64-bit
      systems.