Needless copying in iterations?

[Calvin Spealman]

This is a case where its up to the type involved. For example,
xrange() slices the way you want but range() does not. Maybe a type
would return for slices a proxy object that got the value by index or
maybe it knows that it makes more sense to give you a copy because
changes during the iteration should not be reflected in the iteration.
It would be really easy to make a generic slicer.

On 9/15/07, James Stroud <jstroud 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
> --
> http://mail.python.org/mailman/listinfo/python-list
>


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