[Python-Dev] itertools addition: getitem()

Guido van Rossum guido at python.org
Mon Jul 9 08:33:58 CEST 2007

On 7/9/07, Raymond Hettinger <python at rcn.com> wrote:
> Also, as a practical matter, I think it is a bad idea to introduce
> __getitem__ style access to itertools because the starting point
> moves with each consecutive access:
>     # access items 0, 2, 5, 9, 14, 20, ...
>     for i in range(10):
>         print getitem(iterable, i)
> Worse, this behavior changes depending on whether the iterable
> is re-iterable (a string would yield consecutive items while a
> generator would skip around as shown above).
> Besides being a bug factory, I think the getitem proposal would
> tend to steer people down the wrong road, away from more
> natural solutions to problems involving iterators.  A basic step
> in learning the language is to differentiate between sequences
> and general iterators -- we should not conflate the two.

But doesn't the very same argument also apply against islice(), which
you just offered as an alternative?

PS. If Walter is also at EuroPython, maybe you two could discuss this in person?

--Guido van Rossum (home page: http://www.python.org/~guido/)

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