How to split a sequence according to a predicate?

Question

I very often run into the need to split a sequence into the two subsequences of elements that satisfy and don\'t satisfy a given predicate (preserving the original relative

Answer 1

If you don't care about efficiency, I think groupby (or any "putting data into n bins" functions) has some nice correspondence,

by_bins_iter = itertools.groupby(sorted(data, key=pred), key=pred)
by_bins = dict((k, tuple(v)) for k, v in by_bins_iter)

You can then get to your solution by,

return by_bins.get(True, ()), by_bins.get(False, ())