diff --git a/codes/python/chapter_computational_complexity/leetcode_two_sum.py b/codes/python/chapter_computational_complexity/leetcode_two_sum.py
index e1c0c848c..01c3cbcf1 100644
--- a/codes/python/chapter_computational_complexity/leetcode_two_sum.py
+++ b/codes/python/chapter_computational_complexity/leetcode_two_sum.py
@@ -11,6 +11,7 @@ from include import *
 """ 方法一：暴力枚举 """
 class SolutionBruteForce:
     def twoSum(self, nums: List[int], target: int) -> List[int]:
+        # 两层循环，时间复杂度 O(n^2)
         for i in range(len(nums) - 1):
             for j in range(i + 1, len(nums)):
                 if nums[i] + nums[j] == target:
@@ -20,7 +21,9 @@ class SolutionBruteForce:
 """ 方法二：辅助哈希表 """
 class SolutionHashMap:
     def twoSum(self, nums: List[int], target: int) -> List[int]:
+        # 辅助哈希表，空间复杂度 O(n)
         dic = {}
+        # 单层循环，时间复杂度 O(n)
         for i in range(len(nums)):
             if target - nums[i] in dic:
                 return dic[target - nums[i]], i
diff --git a/codes/python/chapter_computational_complexity/space_complexity.py b/codes/python/chapter_computational_complexity/space_complexity.py
index b4523fedb..46a234a05 100644
--- a/codes/python/chapter_computational_complexity/space_complexity.py
+++ b/codes/python/chapter_computational_complexity/space_complexity.py
@@ -21,7 +21,7 @@ def constant(n):
     node = ListNode(0)
     # 循环中的变量占用 O(1) 空间
     for _ in range(n):
-         c = 0
+        c = 0
     # 循环中的函数占用 O(1) 空间
     for _ in range(n):
         function()
@@ -49,8 +49,8 @@ def quadratic(n):
 """ 平方阶（递归实现） """
 def quadratic_recur(n):
     if n <= 0: return 0
+    # 数组 nums 长度为 n, n-1, ..., 2, 1
     nums = [0] * n
-    print("递归 n =", n, "中的 nums 长度 =", len(nums))
     return quadratic_recur(n - 1)
 
 """ 指数阶（建立满二叉树） """
diff --git a/codes/python/chapter_computational_complexity/worst_best_time_complexity.py b/codes/python/chapter_computational_complexity/worst_best_time_complexity.py
index ed1a9101f..63d14ac72 100644
--- a/codes/python/chapter_computational_complexity/worst_best_time_complexity.py
+++ b/codes/python/chapter_computational_complexity/worst_best_time_complexity.py
@@ -10,7 +10,7 @@ from include import *
 
 """ 生成一个数组，元素为: 1, 2, ..., n ，顺序被打乱 """
 def random_numbers(n):
-    # 生成数组 nums =: 1, 2, 3, ..., n 
+    # 生成数组 nums =: 1, 2, 3, ..., n
     nums = [i for i in range(1, n + 1)]
     # 随机打乱数组元素
     random.shuffle(nums)
diff --git a/codes/python/chapter_sorting/merge_sort.py b/codes/python/chapter_sorting/merge_sort.py
index 5fa7d83a9..437126632 100644
--- a/codes/python/chapter_sorting/merge_sort.py
+++ b/codes/python/chapter_sorting/merge_sort.py
@@ -8,11 +8,10 @@ import sys, os.path as osp
 sys.path.append(osp.dirname(osp.dirname(osp.abspath(__file__))))
 from include import *
 
-"""
-合并左子数组和右子数组
-左子数组区间 [left, mid]
-右子数组区间 [mid + 1, right]
-"""
+
+""" 合并左子数组和右子数组 """
+# 左子数组区间 [left, mid]
+# 右子数组区间 [mid + 1, right]
 def merge(nums, left, mid, right):
     # 初始化辅助数组 借助 copy模块
     tmp = nums[left:right + 1]