[Python-Dev] metaclass insanity
Just van Rossum
just@letterror.com
Tue, 5 Nov 2002 16:08:51 +0100
[JvR]
> > 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.
[later]
> 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
"yield".
Just