Proposal: [... for ... while cond(x)]

[Hugo Ferreira]

I actually like the proposal...
If the argument to remove map, lambda and filter can be that list
comprehension is more "readable", then why can't this one also use it?

Which reminds me this discussion:
http://awkly.org/archive/can-python-take-advantage-of-mapreduce/

Cheers!

Hugo

On 8/6/06, Slawomir Nowaczyk <slawomir.nowaczyk.847 at student.lu.se> wrote:
>
> On Sun, 06 Aug 2006 18:59:39 +0000 (GMT)
> Duncan Booth <duncan.booth at invalid.invalid> wrote:
>
> #> >> > I suggest a new extension of the list comprehension syntax:
> #> >> >
> #> >> > [x for x in xs while cond(x)]
> #> >> >
> #> >> > which would be equivalent to
> #> >> >
> #> >> > list(itertools.takewhile(cond, xs))
> #> >>
> #> >> What would this syntax offer that:
> #> >>
> #> >>    [x for x in takewhile(cond, xs)]
> #> >>
> #> >> doesn't currently offer?
> #> >
> #> > The same thing that [f(x) for x in xs] offers that map(f, xs)
> doesn't,
> #> > and the same thing that [x for x in xs if f(x)] offers that filter(f,
> #> > xs) doesn't. It's more "pythonic". You can use an expression for cond
> #> > instead of a lambda.
> #> >
> #> No, the list comprehension lets you write an expression directly
> #> avoiding a function call, and it also allows you to add in a
> #> condition which can be used to filer the sequence.
>
> I am not sure if I understand you correctly, but... Does it?
>
> >>> a = [0,1,2,3,7,8,9]
> >>> [x for x in takewhile(lambda x: x in a, range(10))]
> [0, 1, 2, 3]
> >>> [x for x in takewhile(x in a, range(10))]
> Traceback (most recent call last):
>   File "<stdin>", line 1, in ?
> TypeError: 'bool' object is not callable
>
> Did I miss something? Notice that using "if" gives different result:
>
> >>> [x for x in range(10) if x in a]
> [0, 1, 2, 3, 7, 8, 9]
>
> #> Your proposal adds nothing.
>
> Well, I am not sure how useful the proposal really is, but it seems to
> add *something* if it would allow for things like:
> [x for x in range(10) while x in a]
>
> --
> Best wishes,
>    Slawomir Nowaczyk
>      ( Slawomir.Nowaczyk at cs.lth.se )
>
> Women who seek to be equal to men lack ambition.
>
> --
> http://mail.python.org/mailman/listinfo/python-list
>



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