> From: Ka-Ping Yee [mailto:ping@zesty.ca]
>
> It's just not the way i expect for-loops to work. Perhaps we would
> need to survey people for objective data, but i feel that most people
> would be surprised if
>
> for x in y: print x
> for x in y: print x
>
> did not print the same thing twice, or if
>
> if x in y: print 'got it'
> if x in y: print 'got it'
>
> did not do the same thing twice. I realize this is my own opinion,
> but it's a fairly strong impression i have.
>
> Well, for a generator, there is no underlying sequence.
>
> while 1: print next(gen)
>
> makes it clear that there is no sequence, but
>
> for x in gen: print x
>
> seems to give me the impression that there is.
I think this is the crux of the matter. You see for: loops as inherently
non-destructive - that they operate on containers. I (and presumably Guido,
though I would never presume to channel him ;) see for: loops as inherently
destructive - that they operate on iterators. That they obtain an iterator
from a container (if possible) is a useful convenience.
Perhaps the terminology is confusing. Consider a queue.
for each person in the queue:
service the person
Is there anyone who would *not* consider this to be destructive (of the
queue)?
Tim Delaney
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