# Iterator Protocol

There are two functions specifically for working with iterators.

int PyIter_Check(PyObject *o)
  Part of the Stable ABI since version 3.8.

  Return non-zero if the object o can be safely passed to `PyIter_Next()`, and `0` otherwise. This function always succeeds.

int PyAIter_Check(PyObject *o)
  Part of the Stable ABI since version 3.10.

  Return non-zero if the object o provides the `AsyncIterator` protocol, and `0` otherwise. This function always succeeds.

  New in version 3.10.

PyObject *PyIter_Next(PyObject *o)
  Return value: New reference. Part of the Stable ABI.

  Return the next value from the iterator o. The object must be an iterator according to `PyIter_Check()` (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 */
    }

type PySendResult

  The enum value used to represent different results of `PyIter_Send()`.

  New in version 3.10.

PySendResult PyIter_Send(PyObject *iter, PyObject *arg, PyObject **presult)
  Part of the Stable ABI since version 3.10.

  Sends the arg value into the iterator iter. Returns:

  - `PYGEN_RETURN` if iterator returns. Return value is returned via presult.

  - `PYGEN_NEXT` if iterator yields. Yielded value is returned via presult.

  - `PYGEN_ERROR` if iterator has raised and exception. presult is set to `NULL`.

  New in version 3.10.