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.. highlightlang:: c
.. _iterator:
Iterator Protocol
=================
.. versionadded:: 2.2
There are two functions specifically for working with iterators.
.. c:function:: int PyIter_Check(PyObject *o)
Return true if the object *o* supports the iterator protocol.
This function can return a false positive in the case of old-style
classes because those classes always define a :c:member:`tp_iternext`
slot with logic that either invokes a :meth:`next` method or raises
a :exc:`TypeError`.
.. c:function:: PyObject* PyIter_Next(PyObject *o)
Return the next value from the iteration *o*. The object must be an iterator
(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 */
}
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