mirror of https://github.com/python/cpython
127 lines
4.5 KiB
ReStructuredText
127 lines
4.5 KiB
ReStructuredText
.. highlight:: c
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.. _slice-objects:
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Slice Objects
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-------------
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.. c:var:: PyTypeObject PySlice_Type
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The type object for slice objects. This is the same as :class:`slice` in the
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Python layer.
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.. c:function:: int PySlice_Check(PyObject *ob)
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Return true if *ob* is a slice object; *ob* must not be ``NULL``. This
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function always succeeds.
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.. c:function:: PyObject* PySlice_New(PyObject *start, PyObject *stop, PyObject *step)
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Return a new slice object with the given values. The *start*, *stop*, and
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*step* parameters are used as the values of the slice object attributes of
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the same names. Any of the values may be ``NULL``, in which case the
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``None`` will be used for the corresponding attribute. Return ``NULL`` if
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the new object could not be allocated.
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.. c:function:: int PySlice_GetIndices(PyObject *slice, Py_ssize_t length, Py_ssize_t *start, Py_ssize_t *stop, Py_ssize_t *step)
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Retrieve the start, stop and step indices from the slice object *slice*,
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assuming a sequence of length *length*. Treats indices greater than
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*length* as errors.
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Returns ``0`` on success and ``-1`` on error with no exception set (unless one of
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the indices was not ``None`` and failed to be converted to an integer,
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in which case ``-1`` is returned with an exception set).
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You probably do not want to use this function.
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.. versionchanged:: 3.2
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The parameter type for the *slice* parameter was ``PySliceObject*``
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before.
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.. 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)
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Usable replacement for :c:func:`PySlice_GetIndices`. Retrieve the start,
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stop, and step indices from the slice object *slice* assuming a sequence of
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length *length*, and store the length of the slice in *slicelength*. Out
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of bounds indices are clipped in a manner consistent with the handling of
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normal slices.
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Returns ``0`` on success and ``-1`` on error with exception set.
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.. note::
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This function is considered not safe for resizable sequences.
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Its invocation should be replaced by a combination of
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:c:func:`PySlice_Unpack` and :c:func:`PySlice_AdjustIndices` where ::
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if (PySlice_GetIndicesEx(slice, length, &start, &stop, &step, &slicelength) < 0) {
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// return error
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}
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is replaced by ::
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if (PySlice_Unpack(slice, &start, &stop, &step) < 0) {
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// return error
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}
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slicelength = PySlice_AdjustIndices(length, &start, &stop, step);
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.. versionchanged:: 3.2
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The parameter type for the *slice* parameter was ``PySliceObject*``
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before.
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.. versionchanged:: 3.6.1
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If ``Py_LIMITED_API`` is not set or set to the value between ``0x03050400``
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and ``0x03060000`` (not including) or ``0x03060100`` or higher
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:c:func:`!PySlice_GetIndicesEx` is implemented as a macro using
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:c:func:`!PySlice_Unpack` and :c:func:`!PySlice_AdjustIndices`.
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Arguments *start*, *stop* and *step* are evaluated more than once.
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.. deprecated:: 3.6.1
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If ``Py_LIMITED_API`` is set to the value less than ``0x03050400`` or
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between ``0x03060000`` and ``0x03060100`` (not including)
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:c:func:`!PySlice_GetIndicesEx` is a deprecated function.
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.. c:function:: int PySlice_Unpack(PyObject *slice, Py_ssize_t *start, Py_ssize_t *stop, Py_ssize_t *step)
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Extract the start, stop and step data members from a slice object as
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C integers. Silently reduce values larger than ``PY_SSIZE_T_MAX`` to
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``PY_SSIZE_T_MAX``, silently boost the start and stop values less than
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``PY_SSIZE_T_MIN`` to ``PY_SSIZE_T_MIN``, and silently boost the step
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values less than ``-PY_SSIZE_T_MAX`` to ``-PY_SSIZE_T_MAX``.
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Return ``-1`` on error, ``0`` on success.
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.. versionadded:: 3.6.1
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.. c:function:: Py_ssize_t PySlice_AdjustIndices(Py_ssize_t length, Py_ssize_t *start, Py_ssize_t *stop, Py_ssize_t step)
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Adjust start/end slice indices assuming a sequence of the specified length.
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Out of bounds indices are clipped in a manner consistent with the handling
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of normal slices.
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Return the length of the slice. Always successful. Doesn't call Python
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code.
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.. versionadded:: 3.6.1
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Ellipsis Object
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^^^^^^^^^^^^^^^
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.. c:var:: PyObject *Py_Ellipsis
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The Python ``Ellipsis`` object. This object has no methods. Like
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:c:data:`Py_None`, it is an `immortal <https://peps.python.org/pep-0683/>`_.
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singleton object.
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.. versionchanged:: 3.12
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:c:data:`Py_Ellipsis` is immortal.
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