.. highlight:: c
.. _sequence:
Sequence Protocol
=================
.. c:function:: int PySequence_Check(PyObject *o)
Return ``1`` if the object provides the sequence protocol, and ``0`` otherwise.
Note that it returns ``1`` for Python classes with a :meth:`__getitem__`
method, unless they are :class:`dict` subclasses, since in general it
is impossible to determine what type of keys the class supports. This
function always succeeds.
.. c:function:: Py_ssize_t PySequence_Size(PyObject *o)
Py_ssize_t PySequence_Length(PyObject *o)
.. index:: builtin: len
Returns the number of objects in sequence *o* on success, and ``-1`` on
failure. This is equivalent to the Python expression ``len(o)``.
.. c:function:: PyObject* PySequence_Concat(PyObject *o1, PyObject *o2)
Return the concatenation of *o1* and *o2* on success, and ``NULL`` on failure.
This is the equivalent of the Python expression ``o1 + o2``.
.. c:function:: PyObject* PySequence_Repeat(PyObject *o, Py_ssize_t count)
Return the result of repeating sequence object *o* *count* times, or ``NULL`` on
failure. This is the equivalent of the Python expression ``o * count``.
.. c:function:: PyObject* PySequence_InPlaceConcat(PyObject *o1, PyObject *o2)
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``.
.. c:function:: PyObject* PySequence_InPlaceRepeat(PyObject *o, Py_ssize_t count)
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``.
.. c:function:: PyObject* PySequence_GetItem(PyObject *o, Py_ssize_t i)
Return the *i*\ th element of *o*, or ``NULL`` on failure. This is the equivalent of
the Python expression ``o[i]``.
.. c:function:: PyObject* PySequence_GetSlice(PyObject *o, Py_ssize_t i1, Py_ssize_t i2)
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]``.
.. c:function:: int PySequence_SetItem(PyObject *o, Py_ssize_t i, PyObject *v)
Assign object *v* to the *i*\ th element of *o*. Raise an exception
and return ``-1`` on failure; return ``0`` on success. This
is the equivalent of the Python statement ``o[i] = v``. This function *does
not* steal a reference to *v*.
If *v* is ``NULL``, the element is deleted, but this feature is
deprecated in favour of using :c:func:`PySequence_DelItem`.
.. c:function:: 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]``.
.. c:function:: 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``.
.. c:function:: 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]``.
.. c:function:: 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)``.
.. c:function:: 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``.
.. c:function:: 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)``.
.. c:function:: PyObject* PySequence_List(PyObject *o)
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)``.
.. c:function:: PyObject* PySequence_Tuple(PyObject *o)
.. index:: builtin: tuple
Return a tuple object with the same contents as the sequence or iterable *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)``.
.. c:function:: PyObject* PySequence_Fast(PyObject *o, const char *m)
Return the sequence or iterable *o* as an object usable by the other
``PySequence_Fast*`` family of functions. If the object is not a sequence or
iterable, raises :exc:`TypeError` with *m* as the message text. Returns
``NULL`` on failure.
The ``PySequence_Fast*`` functions are thus named because they assume
*o* is a :c:type:`PyTupleObject` or a :c:type:`PyListObject` and access
the data fields of *o* directly.
As a CPython implementation detail, if *o* is already a sequence or list, it
will be returned.
.. c:function:: Py_ssize_t PySequence_Fast_GET_SIZE(PyObject *o)
Returns the length of *o*, assuming that *o* was returned by
:c:func:`PySequence_Fast` and that *o* is not ``NULL``. The size can also be
retrieved by calling :c:func:`PySequence_Size` on *o*, but
:c:func:`PySequence_Fast_GET_SIZE` is faster because it can assume *o* is a
list or tuple.
.. c:function:: PyObject* PySequence_Fast_GET_ITEM(PyObject *o, Py_ssize_t i)
Return the *i*\ th element of *o*, assuming that *o* was returned by
:c:func:`PySequence_Fast`, *o* is not ``NULL``, and that *i* is within bounds.
.. c:function:: PyObject** PySequence_Fast_ITEMS(PyObject *o)
Return the underlying array of PyObject pointers. Assumes that *o* was returned
by :c:func:`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.
.. c:function:: PyObject* PySequence_ITEM(PyObject *o, Py_ssize_t i)
Return the *i*\ th element of *o* or ``NULL`` on failure. Faster form of
:c:func:`PySequence_GetItem` but without checking that
:c:func:`PySequence_Check` on *o* is true and without adjustment for negative
indices.
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