[Python-Dev] metaclass insanity

Just van Rossum just@letterror.com
Tue, 5 Nov 2002 16:08:51 +0100

> > class Outer:
> >     [snip snip]
> >     def __iter__(self):
> >         while not self.isAtEnd():
> >             result = self.outer.currentState()
> >             self.outer.advanceState()
> >             yield result

[David Abrahams]
> This only works for 'self-iterable' types like files, right?

No, the generator-iterator can hold state in the form of local variables. That
isn't used in this example, though.

> Hey, wait a sec!
> It doesn't surprise me at all that the above is more compact. I don't
> see any next() interface, nor any raising of StopIteration. Does it
> really satisfy the iterator protocol?

Heh, yeah, that's what generators do. You call a generator-function (like the
__iter__() method above) and it returns a generator-iterator. The magic word is