[Python-Dev] Single- vs. Multi-pass iterability

[David Abrahams]

From: "Andrew Koenig" <ark@research.att.com>


> David> Just replace 'names' by breadth_first and 'numbers' by
depth_first.
>
> David> or-vice-versa-ly y'rs,
>
> which doesn't address the question of a uniform convention.

I'm with you on the desire to have a way to get a
multipass-iterator-or-error in one swell foop. That says "I want to iterate
over this thing without changing it". I still think that hasattr(iter(x),
'__copy__') is a pretty clean way to do that, despite the fact that it
potentially creates an iterator (which some people apparently view as too
heavyweight as an introspection step).

However, I don't see any point in trying to define a protocol for every
different possible iteration view of a thing. Dicts have keys, values, and
items. Trees have breadth-first, depth-first, inorder, postorder, blah,
blah, blah. There are just too many of these, and they're all different.

-Dave