[Python-ideas] Consider making enumerate a sequence if its argument is a sequence

[Random832]

On Thu, Oct 1, 2015, at 14:29, Chris Barker wrote:
> But if why do you need to know that something is an iterable, but NOT an
> iterator? isn't that an implementation detail?

Because an iterator *cannot possibly* allow you to loop through the
contents twice [either one after the other or in parallel], whereas
*most* non-iterator iterables do allow this. This (among other things
such as representing a well-defined finite bag of values) is the
property we're really chasing, "non-iterator iterable" is just a clumsy
and inaccurate way of saying it.

(I'm actually moderately disappointed, incidentally, that there's no
easy way to create e.g. an iterable that will spin up a fresh copy of
the same generator each time it's called. But it's easy enough to make a
decorator for that.)