Iterator Protocol

.. highlightlang:: c

.. versionadded:: 2.2

There are only a couple of functions specifically for working with iterators.

.. cfunction:: int PyIter_Check(PyObject *o)

   Return true if the object *o* supports the iterator protocol.

.. cfunction:: PyObject* PyIter_Next(PyObject *o)

   Return the next value from the iteration *o*.  If the object is an iterator,
   this retrieves the next value from the iteration, and returns *NULL* with no
   exception set if there are no remaining items.  If the object is not an
   iterator, :exc:`TypeError` is raised, or if there is an error in 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 */
}