Alex Martelli wrote: > It's a bit late for 2.5, of course, but, I thought I'd propose it > anyway -- I noticed it on c.l.py. > > In 2.3/2.4 we have many ways to generate and process iterators but > few "accumulators" -- functions that accept an iterable and produce > some kind of "summary result" from it. sum, min, max, for example. > And any, all in 2.5. > > The proposed function tally accepts an iterable whose items are > hashable and returns a dict mapping each item to its count (number of > times it appears). > > This is quite general and simple at the same time: for example, it > was proposed originally to answer some complaint about any and all > giving no indication of the count of true/false items: > > tally(bool(x) for x in seq) > > would give a dict with two entries, counts of true and false items. > > Just like the other accumulators mentioned above, tally is simple to > implement, especially with the new collections.defaultdict: > > import collections > def tally(seq): > d = collections.defaultdict(int) > for item in seq: > d[item] += 1 > return dict(d)
Or: import collections bag = collections.Bag([1, 2, 3, 2, 1]) assert bag.count(1) == 2 assert bag.count(0) == 0 assert 3 in bag # etc... -- Ian Bicking / [EMAIL PROTECTED] / http://blog.ianbicking.org _______________________________________________ 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
