On Apr 4, 2006, at 10:53 PM, Jess Austin wrote: > Alex wrote: >> import collections >> def tally(seq): >> d = collections.defaultdict(int) >> for item in seq: >> d[item] += 1 >> return dict(d) > > I'll stop lurking and submit the following: > > def tally(seq): > return dict((group[0], len(tuple(group[1]))) > for group in itertools.groupby(sorted(seq))) > > In general itertools.groupby() seems like a very clean way to do this > sort of thing, whether you want to end up with a dict or not. I'll go > so far as to suggest that the existence of groupby() obviates the > proposed tally(). Maybe I've just coded too much SQL and it has > warped > my brain... > > OTOH the latter definition of tally won't cope with iterables, and it > seems like O(nlogn) rather than O(n).
It will cope with any iterable just fine (not sure why you think otherwise), but the major big-O impact seems to me to rule it out as a general solution. Alex _______________________________________________ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
