bambam wrote: >> The reason that lists don't have set-like methods is because >> lists aren't sets -- lists can contain duplicate elements and they are ordered. I'd have used sets if I was sure you meant [1,2,3] to mean the same thing as [3,1,2] and no duplicates.
> Interesting point -- if that's all there is in it, then lists should > have difference and intersection methods. Not because they > are the same as sets -- because they are slightly different than > sets. In this case it doesn't matter - my lists don't contain > duplicate elements this time - but I have worked with lists in > money market and in inventory, and finding the intersection > and difference for matching off and netting out are standard > operations. Here you seem to be talking about multisets (also called bags). They have more fully defined algebraic properties analogous to sets. bag([1,2,3,3,4]) == bag([3,1,2,4,3]) != bag([1,2,3,4]) bag([1,2,2,3]) - bag([1,2]) == bag([2,3]) bag([1,2,3]) - bag([3,4]) == bag([1]) >>> Excellent. By symmetry, I see that "list" casts the set back into a list. Some will say 'sorted' is a better conversion of a set to list, since the result is well-defined. --Scott David Daniels [EMAIL PROTECTED] -- http://mail.python.org/mailman/listinfo/python-list
