Protocolo iterador
******************

Hay dos funciones específicas para trabajar con iteradores.

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.

   Added 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.

Para escribir un bucle que itera sobre un iterador, el código en C
debería verse así:

   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

   El valor de enumeración utilizado para representar diferentes
   resultados de "PyIter_Send()".

   Added in version 3.10.

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

   Envía el valor *arg* al iterador *iter*. Retorna:

   * "PYGEN_RETURN" si el iterador regresa. El valor de retorno se
     retorna a través de *presult*.

   * "PYGEN_NEXT" si el iterador cede. El valor cedido se retorna a
     través de *presult*.

   * "PYGEN_ERROR" si el iterador ha lanzado una excepción. *presult*
     se establece en "NULL".

   Added in version 3.10.
