[Tutor] List comprehension for dicts?

[Steven D'Aprano]

On Fri, 20 Aug 2010 06:10:59 pm Alan Gauld wrote:
> "Steven D'Aprano" <steve at pearwood.info> wrote
>
> > the purpose). No matter how fast you can perform a loop, it's
> > always faster to avoid it altogether, so this:
> >
> > seq = xrange(10000000)
> > result = []
> > for i in seq:
> >    if i >= 10: break
> >    result.append(i%2)
> >
> >
> > will be much faster than this:
> >
> > seq = xrange(10000000)
> > result = [i%2 for i in seq if i < 10]
>
> Although it should be pointed out that these are doing very different
> things.

Well yes, but I pointed out that you *can* bail out early of for-loops, 
but not list comprehensions. The whole point is with a list comp, 
you're forced to iterate over the entire sequence, even if you know 
that you're done and would like to exit.



-- 
Steven D'Aprano