[Python-Dev] Re: PEP 322: Reverse Iteration

Phillip J. Eby pje at telecommunity.com
Wed Nov 5 12:02:09 EST 2003

At 07:28 AM 11/5/03 -0800, Guido van Rossum wrote:
> > Why not change enumerate() to return an iterable, rather than an
> > iterator?  Then its __reversed__ method could attempt to delegate to
> > the underlying iterable.  Is it likely that anyone relies on
> > enumerate() being an iterator, rather than an iterable?
>I find it rather elegant to use enumerate() on a file to generate line
>numbers and lines together (adding 1 to the index to produce a more
>conventional line number).  What's more elegant than
>   for i, line in enumerate(f):
>       print i+1, line,
>to print a file with line numbers???  I've used this in throwaway
>code at least, and would hate to lose it.

I thought 'for x in y' always called 'iter(y)', in which case the above 
still works.  It's only this:

ef = enumerate(f)

while 1:
         i,line = ef.next()
         print i+1, line,
     except StopIteration:

That would break.

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