Alan Gauld wrote: > "Chris Calloway" <[EMAIL PROTECTED]> wrote > >>>>> dbs = set(['oracle','mysql','postgres','infomix','access']) >>>>> mine = set(['oracle','mysql','bdb']) >>>>> dbs & mine >> set(['oracle', 'mysql']) >>>>> dbs - mine >> set(['access', 'infomix', 'postgres']) > > Interesting. I didn't know about the & and - set operations. > Thanks for the pointer.
They just invoke special methods, of course: s.issubset(t) s <= t __le__ s.issuperset(t) s >= t __ge__ s.union(t) s | t __or__ s.intersection(t) s & t __and__ s.difference(t) s - t __sub__ s.symmetric_difference(t) s ^ t __xor__ s.update(t) s |= t __ior__ s.intersection_update(t) s &= t __iand__ s.difference_update(t) s -= t __isub__ s.symmetric_difference_update(t) s ^= t __ixor__ Good times! The advantage of the s.method(t) versions are, in Python 2.3.1 and after, they will accept any, cough, iterable as argument t, whereas the operator versions require set objects on both side of the operator: >>> set(xrange(10)).issubset(xrange(20)) True >>> -- Sincerely, Chris Calloway http://www.seacoos.org office: 332 Chapman Hall phone: (919) 962-4323 mail: Campus Box #3300, UNC-CH, Chapel Hill, NC 27599 _______________________________________________ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
