切片物件
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PyTypeObject PySlice_Type

   The type object for slice objects.  This is the same as "slice" in
   the Python layer.

int PySlice_Check(PyObject *ob)

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

PyObject* PySlice_New(PyObject *start, PyObject *stop, PyObject *step)
    *Return value: New reference.*

   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.

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 "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.

   3.2 版更變: The parameter type for the *slice* parameter was
   "PySliceObject*" before.

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 "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.

   備註: This function is considered not safe for resizable
     sequences. Its invocation should be replaced by a combination of
     "PySlice_Unpack()" and "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);

   3.2 版更變: The parameter type for the *slice* parameter was
   "PySliceObject*" before.

   3.6.1 版更變: If "Py_LIMITED_API" is not set or set to the value
   between "0x03050400" and "0x03060000" (not including) or
   "0x03060100" or higher "PySlice_GetIndicesEx()" is implemented as a
   macro using "PySlice_Unpack()" and "PySlice_AdjustIndices()".
   Arguments *start*, *stop* and *step* are evaluated more than once.

   3.6.1 版後已棄用: If "Py_LIMITED_API" is set to the value less than
   "0x03050400" or between "0x03060000" and "0x03060100" (not
   including) "PySlice_GetIndicesEx()" is a deprecated 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.

   3.6.1 版新加入.

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.

   3.6.1 版新加入.


Ellipsis Object
***************

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 "Py_None" it is a singleton object.
