Slice Objects — Python 3.9.23 documentation

# Slice Objects

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`. This function always succeeds.

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.

  Changed in version 3.2: 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.

  Note

  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);

  Changed in version 3.2: The parameter type for the slice parameter was `PySliceObject*` before.

  Changed in version 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 `PySlice_GetIndicesEx()` is implemented as a macro using `PySlice_Unpack()` and `PySlice_AdjustIndices()`. Arguments start, stop and step are evaluated more than once.

  Deprecated since version 3.6.1: 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.

  New in version 3.6.1.

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.

  New in version 3.6.1.

# 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.