[Python-ideas] while conditional in list comprehension ?? (original) (raw)

Zachary Ware zachary.ware+pyideas at gmail.com
Tue Jan 29 16:34:13 CET 2013

On Jan 29, 2013 9:26 AM, "Oscar Benjamin" <oscar.j.benjamin at gmail.com> wrote:

On 29 January 2013 11:51, yoav glazner <yoavglazner at gmail.com> wrote: > Here is very similar version that works (tested on python27) >>>> def stop(): > next(iter([])) > >>>> list((i if i<50 else stop()) for i in range(100))_ _> [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, > 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, > 40, 41, 42, 43, 44, 45, 46, 47, 48, 49] That's a great idea. You could also do: >>> list(i for i in range(100) if i<50 or stop()) It's a shame it doesn't work for list/set/dict comprehensions, though.

I know I'm showing my ignorance here, but how are list/dict/set comprehensions and generator expressions implemented differently that one's for loop will catch a StopIteration and the others won't? Would it make sense to reimplement list/dict/set comprehensions as an equivalent generator expression passed to the appropriate constructor, and thereby allow the StopIteration trick to work for each of them as well?

Regards,

Zach Ware -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://mail.python.org/pipermail/python-ideas/attachments/20130129/66089f35/attachment.html>

More information about the Python-ideas mailing list