-----Original Message----- From: python-dev-bounces+castironpi=comcast.net@python.org [mailto:python- dev-bounces+castironpi=comcast.net@python.org] On Behalf Of Raymond Hettinger Sent: Friday, May 18, 2007 8:35 PM To: python-dev@python.org Subject: [Python-Dev] Py2.6 buildouts to the set API
Here some ideas that have been proposed for sets:
* New method (proposed by Shane Holloway): s1.isdisjoint(s2). Logically equivalent to "not s1.intersection(s2)" but has an early-out if a common member is found. The speed-up is potentially large given two big sets that may largely overlap or may not intersect at all. There is also a memory savings since a new set does not have to be formed and then thrown away.
It sounds -really- good.
* Additional optional arguments for basic set operations to allow chained operations. For example, s=s1.union(s2, s3, s4) would be logically equivalent to s=s1.union(s2).union(s3).union(s4) but would run faster because no intermediate sets are created, copied, and discarded. It would run as if written: s=s1.copy(); s.update(s2); s.update(s3); s.update(s4).
This pleads for elsewhere adding operation in chains. Sort on multiple keys is addressed by itemgetter (IMO also should be built-in). But dict.update, a list append, a deque pop could use these. When-do-you-ever is out of stock and ships in a week.
* Make sets listenable for changes (proposed by Jason Wells):
s = set(mydata) def callback(s): print 'Set %d now has %d items' % (id(s), len(s)) s.listeners.append(callback) s.add(existing_element) # no callback s.add(new_element) # callback
This one calls for subclassing, a la observer pattern. In that vein, some subclassing operation could use a list of pattern-matching / semantic membership. E.g. def every_add_op( self, op, ***data ): call_a_hook( ***data ) op( ***data ) Rings of ML. Support could be provided with def __init__... for x in ( add, update, intersection_update ): def my_x( self, ***data ): call_a_hook( ***data ) x( ***data ) setattr( self, x, my_x ) But you need to know which operations are destructive/constructive, but we can't go back and annotate the whole stdlib. Though I agree that some level of programmatic interference could be useful. Academic concern which shoots 50-50 in the real world. I may be tempered with too much beauty (Beautiful is better than ugly.), not enough market. You're all in it for money.