On Mon, Jan 28, 2013 at 8:59 AM, Oscar Benjamin <oscar.j.benjamin@gmail.com> wrote:
On 28 January 2013 13:56, Chris Angelico <rosuav@gmail.com> wrote:
On Tue, Jan 29, 2013 at 12:33 AM, Wolfgang Maier <wolfgang.maier@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.
The while syntax definitely reads better, and I would guess that dis could clarify how much more efficient using `if n < 400` would be compared to the lambda. Then again this is a rather uncommon situation and it could be handled with the if syntax. Also, if we recall the zen of python "There should be one-- and preferably only one --obvious way to do it." which is argument enough against the `while` syntax.