On Sun, Apr 20, 2014 at 12:27 PM, Kristján Valur Jónsson <krist...@ccpgames.com> wrote: > Well, "for i in x" and other iteration constructs already call "iter ()" on > their iterable. That's the point. Unless you want to manually iterate using > "next ()" then the distinction between an iterable and an iterator is > academic.
Or unless you iterate over the same thing multiple times, which can happen. P.S.: If Python had intended to support 2.x/3.x polyglots in the first place, would iteritems etc. have been removed? My feeling is "no", in which case they should be re-added, since this is the main supported porting mechanism going forward. -- Devin > -------- Original message -------- > From: Steven D'Aprano > Date:20/04/2014 17:05 (GMT+00:00) > To: python-dev@python.org > Subject: Re: [Python-Dev] PEP 469: Restoring the iterkeys/values/items() > methods > > On Sun, Apr 20, 2014 at 03:07:39PM +0000, Kristján Valur Jónsson wrote: > >> Does one ever use iteritems() et al without first invoking iter() on >> it? > > I can't speak for others, but I never invoke iteritems *with* iter(). > What would be the point? iteritems is documented as returning an > interator. > > # never this > for key, value in iter(mydict.iteritems()): ... > > # but this > for key, value in mydict.iteritems(): ... > > >> I.e. is it important that it is an iterator, rather than an >> iterable? I think we could easily relax that requirement in the pep >> and solve 99% of the use cases. > > And the other 1% of cases would be a land-mine waiting to blow the > user's code up. > > Would it actually solve 99% of the use cases? Or only 90%? Or 50%? How > do you know? > > In Python 2.7 iteritems() etc is documented as returning an iterator. > That's a promise of the language, and people will rely on it. But they > won't be able to rely on that promise in polygot 2+3 code -- exactly the > use-case this PEP is trying to satisfy -- because the promise to return > an iterator will be broken in 3. > > It would be actively misleading, since Python 3's iteritems() would > return a view, not an iter, and it would fail at solving the backwards > compatibility issue since views and iterators are not interchangeable > except for the most basic use of iteration. > > _______________________________________________ > Python-Dev mailing list > Python-Dev@python.org > https://mail.python.org/mailman/listinfo/python-dev > Unsubscribe: > https://mail.python.org/mailman/options/python-dev/kristjan%40ccpgames.com > > _______________________________________________ > Python-Dev mailing list > Python-Dev@python.org > https://mail.python.org/mailman/listinfo/python-dev > Unsubscribe: > https://mail.python.org/mailman/options/python-dev/jeanpierreda%40gmail.com > _______________________________________________ Python-Dev mailing list Python-Dev@python.org https://mail.python.org/mailman/listinfo/python-dev Unsubscribe: https://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
