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