Simple min and max on my computer reliably seems to take less time than the sorted solution, and also makes more sense to read. This is what I would intuitively expect anyway with the overhead of making the array.

  >>> timeit.timeit('x=4; y=3; x, y = sorted([x, y])')
  0.49517297744750977
  >>> timeit.timeit('x=4; y=3; x = min(x,y); y = max(x, y)')
  0.2774021625518799