On Mon, 23 Jan 2006 10:36:55 +0000, Bryan Olson wrote: > Christoph Zwerschke wrote: > [...] >> That may be the main problem to decide whether the cartesian product >> should return a generator or a list. > > The Cartesion product is a set.
And the generalization of mathematical sets in Python can be built-in sets, lists or tuples, depending on what you need. Given that cartesian products tend to be *extremely* large, some sort of iterator is the only practical solution -- even if that's not mathematically pure. > [...] >> That's the other problem. The uses cases (like the password cracker >> example) are very limited and in these cases you can either write nested >> loops or write your own cartesian product. > > Cartesian product is one of the essential operations of > relational algebra; in that context it's widely useful. > By itself, it's usually not what one wants. Google on "Cartesian product python" and you will find thousands of hits. This is something that keeps coming up over and over again. Personally, I think cartesian products, together with permutations and combinations, belong in a module, not built-ins. -- Steven. -- http://mail.python.org/mailman/listinfo/python-list
