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

[Eighty]

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))

+ Since Python favors list comprehensions over map, filter, and reduce,
this would be the preferred way to do this
+ "Takewhile operations" occur often, at least for me
+ I don't think it would break any existing syntax

An analogous syntax for dropwhile would be nice, but I can't think of
one.

This is not a PEP because it's a very simple idea and probably not just
anyone (read: me) can write and submit one. If there has been a PEP for
this, I've missed it; if not, it would be nice if someone wrote one.

Discuss.