任何人都可以告訴我我的合併排序在Python中出了什麼問題？

Question

它給了我以下錯誤，我知道它與左或右數組有時是無關的事實。我只是不知道爲什麼是這樣。錯誤：

File "/Users/lezoudali/Documents/Algorithms/sort.py", line 62, in merge 

    while i < len(left) and j < len(right): 

TypeError: object of type 'NoneType' has no len() 

我的代碼：

from random import randint 

alist = [randint(1,50) for i in range(10)] 

def merge(left, right): 
    i = j = 0 
    result = [] 
    while i < len(left) and j < len(right): 
    if left[i] < right[j]: 
     result.append(left[i]) 
     i += 1 
    else: 
     result.append(right[j]) 
     j += 1 
    while i < len(left): 
    result.append(left[i]) 
    i += 1 
    while j < len(right): 
    result.append(right[j]) 
    j += 1 

def mergesort(alist): 
    if len(alist) == 1: 
    return alist 
    mid = len(alist) // 2 
    left = mergesort(alist[:mid]) 
    right = mergesort(alist[mid:]) 
    return merge(left, right) 

print mergesort(alist) 

Answer 1

原來我不是從合併功能回到我的結果。所以函數返回None，這是我遇到的問題。感謝senderle！

def merge(left, right): 
    i = j = 0 
    result = [] 
    while i < len(left) and j < len(right): 
     if left[i] < right[j]: 
     result.append(left[i]) 
     i += 1 
     else: 
     result.append(right[j]) 
     j += 1 
    while i < len(left): 
     result.append(left[i]) 
     i += 1 
    while j < len(right): 
     result.append(right[j]) 
     j += 1 
    return result