python quicksort

quicksort.py

def qs(arr):
  if not arr:
    return []
  len_arr = len(arr)
  if len_arr <= 1:
    return arr
  
  xs = arr[0]
  smaller = [x for x in arr[1:] if x <= xs]
  larger = [x for x in arr[1:] if x > xs]
  
  return qs(smaller) + [xs] + qs(larger)

a = [12, 1, 0 ,3, 1, 5, 3 ,1, 5, -1, 131, 2, 9]
print(qs(a))