[python] universal set - computing subsets from a set (list)

def subsets(x):  
    if x == []:
        return [[]]
    else:
        s = [x]
        for elem in x:
            tmp = x[:]
            tmp.remove(elem)
            new_sub = subsets(tmp)
            for y in new_sub:  # <-- can't just make it a set(), because lists aren't hashable.
                if y not in s:
                    s.append(y)
        return s
>>> s = [1,2,3]
>>> subsets(s)
[[1, 2, 3], [2, 3], [3], [], [2], [1, 3], [1], [1, 2]]

from http://www.daniweb.com/forums/thread89048.html