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

Ethan Furman ethan at stoneleaf.us
Mon Jan 28 22:43:33 CET 2013

On 01/28/2013 01:22 PM, Wolfgang Maier wrote:

However, currently you could solve tasks like this with itertools.takewhile in the following (almost perl-like) way (I illustrate things with numbers to keep it simpler):

l=[1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23] # now retrieve all numbers from 10 to 19 (combining takewhile and slicing) [n for n in itertools.takewhile(lambda n:n<20,l[len([x for x in itertools.takewhile(lambda x:x<10,l)]):])] Nice, isn't it? If I am not mistaken, then with my suggestion this would at least simplify to: [n for n in l[len([x for x in l while x<10]):] while n<20] Not great either, I admit, but at least it's fun to play this mindgame.

Well, as long as we're dreaming, how about

[n for n in l while 10 <= n < 20]

and somebody (else!) can code to skip until the first condition is met, then keep until the second condition is met, and then stop.

:)

Ethan

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