def perm(arr, pos = 0):
    if pos == len(arr):
        yield arr

    for i in range(pos, len(arr)):
        arr[pos], arr[i] = arr[i], arr[pos]
        for _ in perm(arr, pos + 1): yield _
        arr[pos], arr[i] = arr[i], arr[pos]

for i in perm([1,2,3,4]):
    print i
#//python/8706