On Jul 2, 9:08 pm, Paul Rubin <http://phr...@nospam.invalid> wrote: > 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.
Perhaps true, but it would be a nice convenience (for me) as a built- in written in either Python or C. Although the default case of a bool function would surely be faster. > 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. Faster, but in tests of a few short sequences only 1% so. -Brad -- http://mail.python.org/mailman/listinfo/python-list
