蟒蛇歸併排序實現結果在列表嵌套

Question

我試圖實現合併排序在Python

#!/usr/bin/python 
import math 

def merge_sort(unsorted): 
    if(len(unsorted)<2): 
     return unsorted 
    middle = int(math.floor(len(unsorted)/2)) 
    left = merge_sort(unsorted[0:middle]) 
    right = merge_sort(unsorted[middle:]) 
    return merge(left, right) 

def merge(left, right): 
    results = [] 
    while (len(left) > 0 and len(right) > 0): 
     if(left[0] < right[0]): 
      results.append(left.pop(0)) 
     else: 
      results.append(right.pop(0)) 

    if (len(left) > 0): 
     results.append(left) 
    if (len(right) > 0): 
     results.append(right) 

    return results 

print merge_sort(list('7123')) 

但是我的結果看起來像這樣[['1'], ['2'], ['3'], [['7']]]而不是['7', '1', '2', '3']。

我的語法錯誤是什麼？

Answer 1

使用list.extend這裏：

if (len(left) > 0): 
    results.extend(left) 
if (len(right) > 0): 
    results.extend(right) 

list.append VS list.extend：

>>> lis = [1, 2 , 3] 
>>> lis.append([4, 5]) #appends the whole object at the end of the list 
>>> lis 
[1, 2, 3, [4, 5]] 
>>> lis.extend([6, 7]) #appends individual items from the iterable 
>>> lis 
[1, 2, 3, [4, 5], 6, 7] 

幫助上list.extend：

>>> print list.extend.__doc__ 
L.extend(iterable) -- extend list by appending elements from the iterable