Python Merge Sort

merge-sort.py

def merge(l1, l2):
  result = []
  pos_left = 0 
  pos_right = 0 

  for i in range(len(l1) + len(l2)):
    
    if(pos_left >= len(l1)):
      result = result + l2[pos_right:len(l2)] 
      break
    if(pos_right >= len(l2)):
      result = result + l1[pos_left:len(l1)] 
      break
    elif(l1[pos_left] <= l2[pos_right]):
      result.append(l1[pos_left])
      pos_left = pos_left + 1
    elif(l2[pos_right] <= l1[pos_left]):
      result.append(l2[pos_right])
      pos_right = pos_right + 1

  return result

def split(l):
  length = len(l)
  split_on = length/2

  if(length == 1):
    return l
  else:
    left = split(l[0:split_on])
    right = split(l[split_on:length])
    return merge(left, right)
  
l = [1, 1, 4, 15, 18, 7, 9, 2, 18]

print split(l)