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

Wolfgang Maier wolfgang.maier at biologie.uni-freiburg.de
Tue Jan 29 16:44:01 CET 2013

Oscar Benjamin <oscar.j.benjamin at ...> writes:

On 29 January 2013 11:51, yoav glazner <yoavglazner at ...> 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. Oscar

list(i for i in range(100) if i<50 or stop()) Really (!) nice (and 2x as fast as using itertools.takewhile())!

With the somewhat simpler (suggested earlier by Shane)

def stop(): raise StopIteration

this should become part of the python cookbook!!

Thanks a real lot for working this out, Wolfgang

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