[Python-Dev] itertools addition: getitem()

[Walter Dörwald]

Guido van Rossum wrote:
> 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?

Exactly.

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

Sorry, I won't be at EuroPython.

Servus,
   Walter