.. highlightlang:: c
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.. _iterator:
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Iterator Protocol
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=================
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.. versionadded:: 2.2
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There are two functions specifically for working with iterators.
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.. c:function:: int PyIter_Check(PyObject *o)
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Return true if the object *o* supports the iterator protocol.
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This function can return a false positive in the case of old-style
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classes because those classes always define a :c:member:`tp_iternext`
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slot with logic that either invokes a :meth:`next` method or raises
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a :exc:`TypeError`.
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.. c:function:: PyObject* PyIter_Next(PyObject *o)
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Return the next value from the iteration *o*. The object must be an iterator
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(it is up to the caller to check this). If there are no remaining values,
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returns *NULL* with no exception set. If an error occurs while retrieving
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the item, returns *NULL* and passes along the exception.
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To write a loop which iterates over an iterator, the C code should look
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something like this::
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PyObject *iterator = PyObject_GetIter(obj);
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PyObject *item;
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if (iterator == NULL) {
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/* propagate error */
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}
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while (item = PyIter_Next(iterator)) {
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/* do something with item */
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...
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/* release reference when done */
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Py_DECREF(item);
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}
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Py_DECREF(iterator);
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if (PyErr_Occurred()) {
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/* propagate error */
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}
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else {
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/* continue doing useful work */
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}
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