> The view are iterables. They can be iterated more than once and used in > other operations. > > The transformers should be once-through iterators because they can be > passed once-through interators.
This is important, thank you for pointing it out. > Python's design that iter(iterator) is iterator is extremely handy. > Yes, but it has the unfortunate consequence that an iterator is expected to define def __iter__(self): return self which I saw people *not* doing, supposedly because the official documentation says that it needs to be done, but does not explain why (and the interpreter does not enforce it, and the code works anyway). Moreover, some tutorial authors make it even more difficult with using the terms iterator and iterable interchangeably. A notorious example is this wiki: https://wiki.python.org/moin/Iterator It says: *Here is an *iterator* that returns a random number of 1's: * class RandomIterable: def __iter__(self): return self I remember the time when I started to look into iterators, and frankly, with this wiki article, it took me ages to understand,why do iterables return self in their *__iter__* method. But I think I'm getting off-topic... Again, thanks guys, @Terry and @dn for your explanations, you've made the situation clear. Peter -- https://mail.python.org/mailman/listinfo/python-list
