6.5 Iterator Protocol
Description: Iterator Protocol
Keywords: api

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6.5 Iterator Protocol

New in version 2.2.

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

int `PyIter_Check`( | PyObject *o)

  Return true if the object o supports the iterator protocol.

PyObject* `PyIter_Next`( | PyObject *o)

  Return value: New reference.
  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, `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 */
    }