Protocole d'itération
*********************

Il existe deux fonctions dédiées à l'interaction avec les itérateurs.

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.

Pour écrire une boucle itérant un itérateur, le code C devrait
ressembler à :

   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 */
   }
