list of all possible values

[David Gibb]

Hi guys.

I was thinking about a problem I had: suppose I have a list of
possible values. I want to to have a list of all possible lists of
length n whose values are in that original list.

For example: if my values are ['a', 'b', 'c'], then all possible lists
of length 2 would be: aa, ab, ac, ba, bb, bc, ca, cb, cc.

I created a recursive program to do it, but I was wondering if there
was a better way of doing it (possibly with list comprehensions).

Here's my recursive version:

vals = ['a', 'b', 'c']

def foo(length):
    if length <=0:
        return []
    if length == 1:
        return [[x] for x in vals]
    else:
        return [x + [y] for x in foo(length - 1) for y in vals]

print foo(3)

Thanks,
David