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.. highlight:: c
.. _iterator:
Iterator Protocol
=================
There are two functions specifically for working with iterators.
.. c:function:: int PyIter_Check(PyObject *o)
Return non-zero if the object *o* can be safely passed to
:c:func:`PyIter_Next`, and ``0`` otherwise. This function always succeeds.
.. c:function:: int PyAIter_Check(PyObject *o)
Return non-zero if the object *o* provides the :class:`AsyncIterator`
protocol, and ``0`` otherwise. This function always succeeds.
.. versionadded:: 3.10
.. c:function:: PyObject* PyIter_Next(PyObject *o)
Return the next value from the iterator *o*. The object must be an iterator
according to :c:func:`PyIter_Check` (it is up to the caller to check this).
If there are no remaining values, returns ``NULL`` with no exception set.
If an error occurs while retrieving the item, returns ``NULL`` and passes
along the exception.
To write a loop which iterates over an iterator, the C code should look
something like this::
PyObject *iterator = PyObject_GetIter(obj);
PyObject *item;
if (iterator == NULL) {
/* propagate error */
}
while ((item = PyIter_Next(iterator))) {
/* do something with item */
...
/* release reference when done */
Py_DECREF(item);
}
Py_DECREF(iterator);
if (PyErr_Occurred()) {
/* propagate error */
}
else {
/* continue doing useful work */
}
.. c:type:: PySendResult
The enum value used to represent different results of :c:func:`PyIter_Send`.
.. versionadded:: 3.10
.. c:function:: PySendResult PyIter_Send(PyObject *iter, PyObject *arg, PyObject **presult)
Sends the *arg* value into the iterator *iter*. Returns:
- ``PYGEN_RETURN`` if iterator returns. Return value is returned via *presult*.
- ``PYGEN_NEXT`` if iterator yields. Yielded value is returned via *presult*.
- ``PYGEN_ERROR`` if iterator has raised and exception. *presult* is set to ``NULL``.
.. versionadded:: 3.10
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