2009/1/19 Vitor Bosshard <algor...@yahoo.com> > > > > > ----- Mensaje original ---- > > De: Gerald Britton <gerald.brit...@gmail.com> > > Para: Terry Reedy <tjre...@udel.edu> > > CC: python-dev@python.org > > Enviado: lunes, 19 de enero, 2009 15:03:47 > > Asunto: Re: [Python-Dev] PEP 3142: Add a "while" clause to generator > expressions > > > > Duly noted and thanks for the feedback! (just what I was looking for > > actually). I do disagree with the idea that the proposal, if > > implemented, would make Python harder to learn. Not sure who would > > find it harder. Having to find and use takewhile was harder for me. > > I still find that one counter-intuitive. I would have expected the > > parameters in the reverse order (take something, while something else > > is true). Tripped me up a few times, which got me thinking about an > > alternative. > > > Are you even sure the list comprehension doesn't already shortcut > evaluation? > > This quick test in 2.6 hints otherwise: > > > >>> a = (i for i in range(10) if i**2<10) > >>> a.next() > 0 > >>> a.next() > 1 > >>> a.next() > 2 > >>> a.next() > 3 > >>> a.next() > Traceback (most recent call last): > File "<pyshell#32>", line 1, in <module> > a.next() > StopIteration
Does not prove anything. ---- test.py ---- source = iter(xrange(10)) a = (i for i in source if i**2<10) print list(a) print list(source) ---- output --- $ python /tmp/test.py [0, 1, 2, 3] [] While 'a' is being evaluated, the source iterator is first completely exhausted. If the source iterator is infinite, an infinite loop is created and the program doesn't terminate. > > > ¡Todo sobre la Liga Mexicana de fútbol! Estadisticas, resultados, > calendario, fotos y más:< > http://espanol.sports.yahoo.com/ > _______________________________________________ > Python-Dev mailing list > Python-Dev@python.org > http://mail.python.org/mailman/listinfo/python-dev > Unsubscribe: > http://mail.python.org/mailman/options/python-dev/gjcarneiro%40gmail.com > -- Gustavo J. A. M. Carneiro INESC Porto, Telecommunications and Multimedia Unit "The universe is always one step beyond logic." -- Frank Herbert
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