[Python-3000] Iterators for dict keys, values, and items == annoying :)

[Aahz]

On Thu, Mar 23, 2006, Guido van Rossum wrote:
> On 3/23/06, Brett Cannon <brett at python.org> wrote:
>> 
>> I understand Ian's view since I know I like to pass around iterators
>> for use and that disconnects the iterator from the object that
>> generated it and thus makes it impossible to find out possible info on
>> the data contained without exhausting the iterator compared to just
>> performing data upon the object containing the original the data.
> 
> You shouldn't do that unless you are consciously designing an API that
> must be able to work with in(de)finite sequences or other strange
> things. The itertools library is an example of such an API because (by
> intent) it must work for all iterators.
> 
> Most APIs aren't as constrained and it's fine to require an iterable
> instead of an iterator.

The problem is that prior to Python 2.1, there weren't any iterators;
moreover, my impression is that the majority of the Python community
didn't really "get" iterators until fairly recently.  I think part of
the objection here is that while Py3K is intended to be a point where we
can break backward compatibility, semantic breakage is going to be very
hard to track down in this case.

I'm not really sure where I stand.  I *like* the idea of making d.keys()
return an iterator, but my impression is that it's going to be one of the
more painful changes.
-- 
Aahz (aahz at pythoncraft.com)           <*>         http://www.pythoncraft.com/

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