Brad <schi...@gmail.com> writes:
> On Jul 2, 8:14 pm, Paul Rubin <http://phr...@nospam.invalid> wrote:
> > schickb <schi...@gmail.com> writes:
> > > def split(seq, func=None):
> > > if func is None:
> > > func = bool
> > > t, f = [], []
> > > for item in seq:
> > > if func(item):
> > > t.append(item)
> > > else:
> > > f.append(item)
> > > return (t, f)
> >
> > untested:
> >
> > def split(seq, func=bool):
> > xs = zip(seq, itertools.imap(func, seq))
> > t = list(x for (x,y) in xs if y)
> > f = list(x for (x,y) in xs if not y)
> > return (t, f)
>
> In my testing that is 3.5x slower than the original solution (and less
> clear imo). I fixed my version to take a bool default. Either way, I'm
> not really looking for additional ways to do this in Python unless
> I've totally missed something. What I am considering is writing it in
> C, much like filter.
I'm a little skeptical that the C version will help much, if it's
evaluating a python function at every list element. Here's a variant
of your version:
def split(seq, func=bool):
t, f = [], []
ta, fa = t.append, f.append
for item in seq:
(ta if func(item) else fa)(item)
return (t, f)
This avoids some dict lookups and copying. I wonder if that helps
significantly.
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