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# Sequence Protocol

int `PySequence_Check`(PyObject *o)
  Return `1` if the object provides sequence protocol, and `0` otherwise. This function always succeeds.

Py_ssize_t `PySequence_Size`(PyObject *o)
Py_ssize_t `PySequence_Length`(PyObject *o)

  Returns the number of objects in sequence o on success, and `-1` on failure. For objects that do not provide sequence protocol, this is equivalent to the Python expression `len(o)`.

PyObject* `PySequence_Concat`(PyObject *o1, PyObject *o2)
  Return value: New reference.

  Return the concatenation of o1 and o2 on success, and NULL on failure. This is the equivalent of the Python expression `o1 + o2`.

PyObject* `PySequence_Repeat`(PyObject *o, Py_ssize_t count)
  Return value: New reference.

  Return the result of repeating sequence object o count times, or NULL on failure. This is the equivalent of the Python expression `o * count`.

PyObject* `PySequence_InPlaceConcat`(PyObject *o1, PyObject *o2)
  Return value: New reference.

  Return the concatenation of o1 and o2 on success, and NULL on failure. The operation is done in-place when o1 supports it. This is the equivalent of the Python expression `o1 += o2`.

PyObject* `PySequence_InPlaceRepeat`(PyObject *o, Py_ssize_t count)
  Return value: New reference.

  Return the result of repeating sequence object o count times, or NULL on failure. The operation is done in-place when o supports it. This is the equivalent of the Python expression `o *= count`.

PyObject* `PySequence_GetItem`(PyObject *o, Py_ssize_t i)
  Return value: New reference.

  Return the i*th element of *o, or NULL on failure. This is the equivalent of the Python expression `o[i]`.

PyObject* `PySequence_GetSlice`(PyObject *o, Py_ssize_t i1, Py_ssize_t i2)
  Return value: New reference.

  Return the slice of sequence object o between i1 and i2, or NULL on failure. This is the equivalent of the Python expression `o[i1:i2]`.

int `PySequence_SetItem`(PyObject *o, Py_ssize_t i, PyObject *v)
  Assign object v to the i*th element of *o. Returns `-1` on failure. This is the equivalent of the Python statement `o[i] = v`. This function does not steal a reference to v.

int `PySequence_DelItem`(PyObject *o, Py_ssize_t i)
  Delete the i*th element of object *o. Returns `-1` on failure. This is the equivalent of the Python statement `del o[i]`.

int `PySequence_SetSlice`(PyObject *o, Py_ssize_t i1, Py_ssize_t i2, PyObject *v)
  Assign the sequence object v to the slice in sequence object o from i1 to i2. This is the equivalent of the Python statement `o[i1:i2] = v`.

int `PySequence_DelSlice`(PyObject *o, Py_ssize_t i1, Py_ssize_t i2)
  Delete the slice in sequence object o from i1 to i2. Returns `-1` on failure. This is the equivalent of the Python statement `del o[i1:i2]`.

Py_ssize_t `PySequence_Count`(PyObject *o, PyObject *value)
  Return the number of occurrences of value in o, that is, return the number of keys for which `o[key] == value`. On failure, return `-1`. This is equivalent to the Python expression `o.count(value)`.

int `PySequence_Contains`(PyObject *o, PyObject *value)
  Determine if o contains value. If an item in o is equal to value, return `1`, otherwise return `0`. On error, return `-1`. This is equivalent to the Python expression `value in o`.

Py_ssize_t `PySequence_Index`(PyObject *o, PyObject *value)
  Return the first index i for which `o[i] == value`. On error, return `-1`. This is equivalent to the Python expression `o.index(value)`.

PyObject* `PySequence_List`(PyObject *o)
  Return value: New reference.

  Return a list object with the same contents as the arbitrary sequence o. The returned list is guaranteed to be new.

PyObject* `PySequence_Tuple`(PyObject *o)
  Return value: New reference.

  Return a tuple object with the same contents as the arbitrary sequence o or NULL on failure. If o is a tuple, a new reference will be returned, otherwise a tuple will be constructed with the appropriate contents. This is equivalent to the Python expression `tuple(o)`.

PyObject* `PySequence_Fast`(PyObject *o, const char *m)
  Return value: New reference.

  Returns the sequence o as a tuple, unless it is already a tuple or list, in which case o is returned. Use `PySequence_Fast_GET_ITEM` to access the members of the result. Returns NULL on failure. If the object is not a sequence, raises `TypeError` with m as the message text.

PyObject* `PySequence_Fast_GET_ITEM`(PyObject *o, Py_ssize_t i)
  Return value: Borrowed reference.

  Return the i*th element of *o, assuming that o was returned by `PySequence_Fast`, o is not NULL, and that i is within bounds.

PyObject** `PySequence_Fast_ITEMS`(PyObject *o)

  Return the underlying array of PyObject pointers. Assumes that o was returned by `PySequence_Fast` and o is not NULL.

  Note, if a list gets resized, the reallocation may relocate the items array. So, only use the underlying array pointer in contexts where the sequence cannot change.

PyObject* `PySequence_ITEM`(PyObject *o, Py_ssize_t i)
  Return value: New reference.

  Return the i*th element of *o or NULL on failure. Macro form of `PySequence_GetItem` but without checking that `PySequence_Check(o)` is true and without adjustment for negative indices.

Py_ssize_t `PySequence_Fast_GET_SIZE`(PyObject *o)
  Returns the length of o, assuming that o was returned by `PySequence_Fast` and that o is not NULL. The size can also be gotten by calling `PySequence_Size` on o, but `PySequence_Fast_GET_SIZE` is faster because it can assume o is a list or tuple.

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