Is there an algorithm to find unique combinations of 2 lists? 5 lists?

Question

I have N Lists I\'d like to find unique combinations of. I\'ve written it out on my whiteboard and it all seems to have a pattern, I just haven\'t found it

Answer 1

I'm assuming that you want the Cartesian product - all possible lists created by choosing exactly one element from each list. You can implement it recursively, like this:

def cartesian_product(l):
    if l:
        for b in cartesian_product(l[1:]):
            for a in l[0]:
                yield [a] + b
    else:
        yield []        

l = [
 [ 'a', 'b' ],
 [ 'c', 'd', 'e' ],
 [ 'f', 'g' ],
]

for x in cartesian_product(l):
    print x

Update: ~unutbu's suggestion of itertools.product is better, but I'll leave this here anyway.