Needless copying in iterations?

[buffi]

On Sep 15, 11:58 pm, James Stroud <jstr... at mbi.ucla.edu> wrote:
> Hello all,
>
> I was staring at a segment of code that looked like this today:
>
>     for something in stuff[x:y]:
>       whatever(something)
>
> and was wondering if the compiler really made a copy of the slice from
> stuff as the code seems to suggest, or does it find some way to produce
> an iterator without the need to make a copy (if stuff is a built-in
> sequence type)? Or would it be more efficient to do the more clumsy (in
> my opinion):
>
>     for i in xrange(x, y):
>       whatever(stuff[i])
>
> James

itertools.islice does what you want

import itertools
for something in itertools.islice(stuff, x, y):
      whatever(something)