1.. highlightlang:: c
2
3.. _slice-objects:
4
5Slice Objects
6-------------
7
8
9.. c:var:: PyTypeObject PySlice_Type
10
11   The type object for slice objects.  This is the same as :class:`slice` in the
12   Python layer.
13
14
15.. c:function:: int PySlice_Check(PyObject *ob)
16
17   Return true if *ob* is a slice object; *ob* must not be *NULL*.
18
19
20.. c:function:: PyObject* PySlice_New(PyObject *start, PyObject *stop, PyObject *step)
21
22   Return a new slice object with the given values.  The *start*, *stop*, and
23   *step* parameters are used as the values of the slice object attributes of
24   the same names.  Any of the values may be *NULL*, in which case the
25   ``None`` will be used for the corresponding attribute.  Return *NULL* if
26   the new object could not be allocated.
27
28
29.. c:function:: int PySlice_GetIndices(PyObject *slice, Py_ssize_t length, Py_ssize_t *start, Py_ssize_t *stop, Py_ssize_t *step)
30
31   Retrieve the start, stop and step indices from the slice object *slice*,
32   assuming a sequence of length *length*. Treats indices greater than
33   *length* as errors.
34
35   Returns ``0`` on success and ``-1`` on error with no exception set (unless one of
36   the indices was not :const:`None` and failed to be converted to an integer,
37   in which case ``-1`` is returned with an exception set).
38
39   You probably do not want to use this function.
40
41   .. versionchanged:: 3.2
42      The parameter type for the *slice* parameter was ``PySliceObject*``
43      before.
44
45
46.. 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)
47
48   Usable replacement for :c:func:`PySlice_GetIndices`.  Retrieve the start,
49   stop, and step indices from the slice object *slice* assuming a sequence of
50   length *length*, and store the length of the slice in *slicelength*.  Out
51   of bounds indices are clipped in a manner consistent with the handling of
52   normal slices.
53
54   Returns ``0`` on success and ``-1`` on error with exception set.
55
56   .. note::
57      This function is considered not safe for resizable sequences.
58      Its invocation should be replaced by a combination of
59      :c:func:`PySlice_Unpack` and :c:func:`PySlice_AdjustIndices` where ::
60
61         if (PySlice_GetIndicesEx(slice, length, &start, &stop, &step, &slicelength) < 0) {
62             // return error
63         }
64
65      is replaced by ::
66
67         if (PySlice_Unpack(slice, &start, &stop, &step) < 0) {
68             // return error
69         }
70         slicelength = PySlice_AdjustIndices(length, &start, &stop, step);
71
72   .. versionchanged:: 3.2
73      The parameter type for the *slice* parameter was ``PySliceObject*``
74      before.
75
76   .. versionchanged:: 3.6.1
77      If ``Py_LIMITED_API`` is not set or set to the value between ``0x03050400``
78      and ``0x03060000`` (not including) or ``0x03060100`` or higher
79      :c:func:`!PySlice_GetIndicesEx` is implemented as a macro using
80      :c:func:`!PySlice_Unpack` and :c:func:`!PySlice_AdjustIndices`.
81      Arguments *start*, *stop* and *step* are evaluated more than once.
82
83   .. deprecated:: 3.6.1
84      If ``Py_LIMITED_API`` is set to the value less than ``0x03050400`` or
85      between ``0x03060000`` and ``0x03060100`` (not including)
86      :c:func:`!PySlice_GetIndicesEx` is a deprecated function.
87
88
89.. c:function:: int PySlice_Unpack(PyObject *slice, Py_ssize_t *start, Py_ssize_t *stop, Py_ssize_t *step)
90
91   Extract the start, stop and step data members from a slice object as
92   C integers.  Silently reduce values larger than ``PY_SSIZE_T_MAX`` to
93   ``PY_SSIZE_T_MAX``, silently boost the start and stop values less than
94   ``PY_SSIZE_T_MIN`` to ``PY_SSIZE_T_MIN``, and silently boost the step
95   values less than ``-PY_SSIZE_T_MAX`` to ``-PY_SSIZE_T_MAX``.
96
97   Return ``-1`` on error, ``0`` on success.
98
99   .. versionadded:: 3.6.1
100
101
102.. c:function:: Py_ssize_t PySlice_AdjustIndices(Py_ssize_t length, Py_ssize_t *start, Py_ssize_t *stop, Py_ssize_t step)
103
104   Adjust start/end slice indices assuming a sequence of the specified length.
105   Out of bounds indices are clipped in a manner consistent with the handling
106   of normal slices.
107
108   Return the length of the slice.  Always successful.  Doesn't call Python
109   code.
110
111   .. versionadded:: 3.6.1
112
113
114Ellipsis Object
115---------------
116
117
118.. c:var:: PyObject *Py_Ellipsis
119
120   The Python ``Ellipsis`` object.  This object has no methods.  It needs to be
121   treated just like any other object with respect to reference counts.  Like
122   :c:data:`Py_None` it is a singleton object.
123