# Iterator Protocol

There are two functions specifically for working with iterators.

int `PyIter_Check`(PyObject *o)

  Return true if the object o supports the iterator protocol. This function always succeeds.

PyObject* `PyIter_Next`(PyObject *o)
  Return value: New reference.

  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 */
    }