def print_powerset(a): l = len(a) r = range(l) b = [0] * l while True: print([a[x] for x in r if b[x]]) i = 0 while True: if b[i] == 0: b[i] = 1 break b[i] = 0 i += 1 if i == l: return print_powerset([1, 2, 3, 4, 5])