[Python-ideas] while conditional in list comprehension ??

[Masklinn]

On 2013-01-28, at 14:59 , Oscar Benjamin wrote:

> On 28 January 2013 13:56, Chris Angelico <rosuav at gmail.com> wrote:
>> On Tue, Jan 29, 2013 at 12:33 AM, Wolfgang Maier
>> <wolfgang.maier at biologie.uni-freiburg.de> wrote:
>>> Why not extend this filtering by allowing a while statement in addition to
>>> if, as in:
>>> 
>>> [n for n in range(1,1000) while n < 400]
>> 
>> The time machine strikes again! Check out itertools.takewhile - it can
>> do pretty much that:
>> 
>> import itertools
>> [n for n in itertools.takewhile(lambda n: n<400, range(1,1000))]
>> 
>> It's not quite list comp notation, but it works.
>> 
>>>>> [n for n in itertools.takewhile(lambda n: n<40, range(1,100))]
>> [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]
> 
> The while clause is a lot clearer/nicer than takewhile/lambda.
> Presumably it would be more efficient as well.

Maybe, but it's a rather uncommon need and that way lies Common Lisp's
`loop`.