Hirokazu Yamamoto wrote
> Hmm, but python document says,
> (http://docs.python.org/library/stdtypes.html#typeiter)
>
> >The iterator objects themselves are required to support the
> >following two methods, which together form the iterator protocol:
>
> Is this false information?

Oh, you are right. I got confused by looking at the implementation of
PyIter_Check(), which only verifies that tp_next is not NULL. Anyway, 
_batch_appends() and _batch_setitems() in pickle.py calls iter() on the
iterators; so, the iterators must provide __iter__ too.

Personally, I wouldn't bother about checking for __iter__ to avoid
adding a new method to Pickler and also to save a few hasattr() calls. 
But I have to admit, it is really just nitpicking at this point.