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.. highlightlang:: c
.. _slice-objects:
Slice Objects
-------------
.. c:var:: PyTypeObject PySlice_Type
The type object for slice objects. This is the same as :class:`slice` in the
Python layer.
.. 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(PyObject *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.
.. versionchanged:: 3.2
The parameter type for the *slice* parameter was ``PySliceObject*``
before.
.. c:function:: int PySlice_GetIndicesEx(PyObject *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.
.. note::
This function is considered not safe for resizable sequences.
Its invocation should be replaced by a combination of
:c:func:`PySlice_Unpack` and :c:func:`PySlice_AdjustIndices` where ::
if (PySlice_GetIndicesEx(slice, length, &start, &stop, &step, &slicelength) < 0) {
// return error
}
is replaced by ::
if (PySlice_Unpack(slice, &start, &stop, &step) < 0) {
// return error
}
slicelength = PySlice_AdjustIndices(length, &start, &stop, step);
.. versionchanged:: 3.2
The parameter type for the *slice* parameter was ``PySliceObject*``
before.
.. versionchanged:: 3.6.1
If ``Py_LIMITED_API`` is not set or set to the value between ``0x03050400``
and ``0x03060000`` (not including) or ``0x03060100`` or higher
:c:func:`!PySlice_GetIndicesEx` is implemented as a macro using
:c:func:`!PySlice_Unpack` and :c:func:`!PySlice_AdjustIndices`.
Arguments *start*, *stop* and *step* are evaluated more than once.
.. deprecated:: 3.6.1
If ``Py_LIMITED_API`` is set to the value less than ``0x03050400`` or
between ``0x03060000`` and ``0x03060100`` (not including)
:c:func:`!PySlice_GetIndicesEx` is a deprecated function.
.. c:function:: int PySlice_Unpack(PyObject *slice, Py_ssize_t *start, Py_ssize_t *stop, Py_ssize_t *step)
Extract the start, stop and step data members from a slice object as
C integers. Silently reduce values larger than ``PY_SSIZE_T_MAX`` to
``PY_SSIZE_T_MAX``, silently boost the start and stop values less than
``PY_SSIZE_T_MIN`` to ``PY_SSIZE_T_MIN``, and silently boost the step
values less than ``-PY_SSIZE_T_MAX`` to ``-PY_SSIZE_T_MAX``.
Return ``-1`` on error, ``0`` on success.
.. versionadded:: 3.6.1
.. c:function:: Py_ssize_t PySlice_AdjustIndices(Py_ssize_t length, Py_ssize_t *start, Py_ssize_t *stop, Py_ssize_t step)
Adjust start/end slice indices assuming a sequence of the specified length.
Out of bounds indices are clipped in a manner consistent with the handling
of normal slices.
Return the length of the slice. Always successful. Doesn't call Python
code.
.. versionadded:: 3.6.1
Ellipsis Object
---------------
.. c:var:: PyObject *Py_Ellipsis
The Python ``Ellipsis`` object. This object has no methods. It needs to be
treated just like any other object with respect to reference counts. Like
:c:data:`Py_None` it is a singleton object.
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