"Christian Stapfer" <nil at dev.nul> wrote: > <ajikoe at gmail.com> wrote: > > try to use set. > > Sorting the two lists and then extracting > A-B, B-A, A|B, A & B and A ^ B in one single > pass seems to me very likely to be much faster > for large lists. Why don't you implement it, test it and time it to be more convincing about your intuition ? George