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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 ith 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 ith 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 ith 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 sequence or iterable o, or NULL on failure. The returned list is guaranteed to be new. This is equivalent to the Python expression `list(o)`.

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.

  Return the sequence o as a list, 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 ith 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 ith element of o or NULL on failure. Macro form of `PySequence_GetItem()` but without checking that `PySequence_Check()` on 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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