.. highlightlang:: c

.. _iterator:

Iterator Protocol

=================

.. 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 */

   }