Python: unclechu's quicksort

def quick_sort(a_list):
  if len(a_list) < 2: return a_list
  lesser = quick_sort([x for x in a_list[1:] if x <= a_list[0]])
  bigger = quick_sort([x for x in a_list[1:] if x >  a_list[0]])
  return sum([lesser, [a_list[0]], bigger], [])