all possible combinations

[rbt]

On Wed, 2005-07-13 at 11:09 -0400, rbt wrote:
> On Wed, 2005-07-13 at 10:21 -0400, rbt wrote:
> > Say I have a list that has 3 letters in it:
> > 
> > ['a', 'b', 'c']
> > 
> > I want to print all the possible 4 digit combinations of those 3
> > letters:
> > 
> > 4^3 = 64
> > 
> > aaaa
> > abaa
> > aaba
> > aaab
> > acaa
> > aaca
> > aaac
> > ...
> > 
> > What is the most efficient way to do this? 
> 
> Expanding this to 4^4 (256) to test the random.sample function produces
> interesting results. It never finds more than 24 combinations out of the
> possible 256. This leads to the question... how 'random' is sample ;)
> 
> Try it for yourselves:
> 
> test = list('1234')
> 
> combinations = []
> while 1:
>     combo = random.sample(test, 4)
>     possibility = ''.join(combo)
>     if possibility not in combinations:
>         print possibility    
>         combinations.append(possibility)
>         continue
>     else:
>         continue
> 

Someone pointed out off-list that this is doing permutation, not
combination. Is there a way to make random.sample to do combinations?