diff --git a/1. Python 安装及基本语法.ipynb b/1. Python 安装及基本语法.ipynb
index 545f61c..147966b 100644
--- a/1. Python 安装及基本语法.ipynb	
+++ b/1. Python 安装及基本语法.ipynb	
@@ -497,14 +497,14 @@
     "    - `**` 表示乘方，`1 ** 2` 的结果是 1\n",
     "    - `/` 表示除法，`1 / 2` 的结果是 0.5      \n",
     "    - `//` 表示整除，`1 // 2` 的结果是 0    （相当于除法结果向下取整）\n",
-    "    - `%` 表示取余 `1 % 2` 的结果是 1\n",
+    "    - `%` 表示取余，`1 % 2` 的结果是 1\n",
     "    \n",
     "    \n",
     "- 逻辑运算符\n",
     "    - `>` 表示大于，`1 > 2` 的结果是 False\n",
     "    - `>=` 表示大于等于， `1 >= 2` 的结果是 False\n",
-    "    - `<=` 表示小于，`1 > 2` 的结果是 True\n",
-    "    - `<` 表示小于等于， `1 >= 2` 的结果是 True\n",
+    "    - `<=` 表示小于，`1 <= 2` 的结果是 True\n",
+    "    - `<` 表示小于等于， `1 < 2` 的结果是 True\n",
     "    - `==` 表示等于， `1 == 2` 的结果是 False\n",
     "    - `!=` 表示不等于， `1 != 2` 的结果是 True\n",
     "    - `and` 表示逻辑\"与\"，`True and False` 的结果是 False\n",
@@ -517,11 +517,18 @@
     "    - `<<` 表示左移操作\n",
     "    - `&` 表示按位与\n",
     "    - `|` 表示按位或\n",
-    "    - `^` 表示按位亦或\n",
+    "    - `^` 表示按位异或\n",
     "    - `~` 表示按位取反\n",
     "    \n",
     "其中最常用的是算数运算符与逻辑运算符，位运算符在 集合 操作中经常使用。\n",
-    "    "
+    "\n",
+    "附：逻辑运算参照表\n",
+    "| X     | Y     | X and Y | X or Y | not X | not Y |\n",
+    "| ----- | ----- | ------- | ------ | ----- | ----- |\n",
+    "| True  | True  | True    | True   | False | False |\n",
+    "| True  | False | False   | True   | False | True  |\n",
+    "| False | False | False   | False  | True  | True  |\n",
+    "| False | True  | False   | True   | True  | False |\n"
    ]
   },
   {
@@ -1334,11 +1341,8 @@
   }
  ],
  "metadata": {
-  "interpreter": {
-   "hash": "aee8b7b246df8f9039afb4144a1f6fd8d2ca17a180786b69acc140d282b71a49"
-  },
   "kernelspec": {
-   "display_name": "Python 3",
+   "display_name": "Python 3.7.1 ('DataScience')",
    "language": "python",
    "name": "python3"
   },
@@ -1352,7 +1356,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.9.2"
+   "version": "3.7.1"
   },
   "toc": {
    "base_numbering": 1,
@@ -1366,6 +1370,11 @@
    "toc_position": {},
    "toc_section_display": true,
    "toc_window_display": true
+  },
+  "vscode": {
+   "interpreter": {
+    "hash": "4951620600495571d210fcc70149573e34741e5378bdea11097277e6fa3349d5"
+   }
   }
  },
  "nbformat": 4,
diff --git a/2. Python 数据结构.ipynb b/2. Python 数据结构.ipynb
index 3e5a124..19427aa 100644
--- a/2. Python 数据结构.ipynb	
+++ b/2. Python 数据结构.ipynb	
@@ -15,11 +15,11 @@
    "source": [
     "顾名思义，数据结构是能够将数据组合在一起的一种结构。\n",
     "\n",
-    "在数据科学领域，很多情况下需要将数据进行有序排列。例如我们统计了大学某班 50 人的数学成绩，那么创建 50 个变量例如 XiaoMing = 99, XiaoHu = 86 .... 无疑是非常繁琐的。这时我们可以通过数据结构整合这些数据，例如在上一节中以方括号标识的序列 `[ 99, 86, 77 .... ]`，这将会使我们的程序大大简化。\n",
+    "在数据科学领域，很多情况下需要将数据进行有序排列。例如我们统计了大学某班 50 人的数学成绩，那么创建 50 个变量例如 XiaoMing = 99, XiaoHu = 86 .... 无疑是非常繁琐的。这时我们可以通过数据结构整合这些数据，例如在上一节中以方括号标识的列表 `[ 99, 86, 77 .... ]`，这将会使我们的程序大大简化。\n",
     "\n",
     "Python 中常用的数据结构有：\n",
     "\n",
-    "- 序列 List: 用于保存有序项集合的变量，以方括号标识。\n",
+    "- 列表 List: 用于保存有序项集合的变量，以方括号标识。\n",
     "- 元组 Tuple: 用于保存有序项集合的常量，以圆括号标识。\n",
     "- 字典 Dict: 用于保存无序（键，值）项集合的变量，以花括号标识。\n",
     "- 集合 Set: 用于保存无序项集合的变量，以花括号标识。\n",
@@ -40,7 +40,7 @@
    "id": "according-admission",
    "metadata": {},
    "source": [
-    "## 1.2.1 序列"
+    "## 1.2.1 列表"
    ]
   },
   {
@@ -48,7 +48,7 @@
    "id": "union-medication",
    "metadata": {},
    "source": [
-    "序列是用于保存有序项集合的变量，通过方括号创建。序列是最容易理解的数据结构，它就像一个任务清单，任务清单的每一项都是一个单独的任务。\n",
+    "列表是用于保存有序项集合的变量，通过方括号创建。列表是最容易理解的数据结构，它就像一个任务清单，任务清单的每一项都是一个单独的任务。\n",
     "\n",
     "下面我们创建一个含有四个整数的列表。"
    ]
@@ -69,14 +69,14 @@
    "metadata": {},
    "source": [
     "\n",
-    "序列支持以下操作：\n",
+    "列表支持以下操作：\n",
     "\n",
-    "- 增：通过函数 `append` 可以向序列内增加元素\n",
-    "- 删：通过关键字 `del` 可以删除序列内元素\n",
-    "- 查：通过关键字 `[ ]` 可以查找序列某个位置元素\n",
+    "- 增：通过函数 `append` 可以向列表内增加元素\n",
+    "- 删：通过关键字 `del` 可以删除列表内元素\n",
+    "- 查：通过关键字 `[ ]` 可以查找列表某个位置元素\n",
     "- 改：通过赋值符号 `=` 可以修改某个位置的元素\n",
     "\n",
-    "序列的优点是：\n",
+    "列表的优点是：\n",
     "\n",
     "- 快速向尾部添加元素\n",
     "- 快速遍历所有元素\n",
@@ -96,9 +96,9 @@
    "id": "stretch-newsletter",
    "metadata": {},
    "source": [
-    "我们通过 `[ ]` 关键字查找序列中某个位置的元素。\n",
+    "我们通过 `[ ]` 关键字查找列表中某个位置的元素。\n",
     "\n",
-    "例如 `l[0]` 可以获取序列中首个元素，`l[1]` 可以获取序列中第 2 个元素。同时它还支持倒序查找，例如 `l[-1]` 表示倒数第一个元素（末尾的元素）。"
+    "例如 `l[0]` 可以获取列表中首个元素，`l[1]` 可以获取列表中第 2 个元素。同时它还支持倒序查找，例如 `l[-1]` 表示倒数第一个元素（末尾的元素）。"
    ]
   },
   {
@@ -134,9 +134,9 @@
    "id": "photographic-worker",
    "metadata": {},
    "source": [
-    "`[ ]` 关键字也可以通过 “切片” 的形式获取含有多个元素的子序列。\n",
+    "`[ ]` 关键字也可以通过 “切片” 的形式获取含有多个元素的子列表。\n",
     "\n",
-    "例如 `l[0:2]` 代表序列从中第 0 个元素 到 第 2 个元素（前开后闭，不包括第 2 个元素）"
+    "例如 `l[0:2]` 代表列表从中第 0 个元素 到 第 2 个元素（左闭右开 `[ ) `，不包括第 2 个元素）"
    ]
   },
   {
@@ -155,9 +155,9 @@
     }
    ],
    "source": [
-    "## 查找第 0 到 第 2 的元素子序列\n",
+    "## 查找第 0 到 第 2 的元素子列表\n",
     "print(l[0:2])\n",
-    "## 查找第 1 到 最后 的元素子序列\n",
+    "## 查找第 1 到 最后 的元素子列表\n",
     "print(l[1:-1])"
    ]
   },
@@ -174,7 +174,7 @@
    "id": "alien-appeal",
    "metadata": {},
    "source": [
-    "通过 `[ ]` 关键字同样可以修改序列中某个位置的元素，类似的它也支持倒序以及切片的形式。"
+    "通过 `[ ]` 关键字同样可以修改列表中某个位置的元素，类似的它也支持倒序以及切片的形式。"
    ]
   },
   {
@@ -212,7 +212,7 @@
     }
    ],
    "source": [
-    "## 修改从第 0 到第 2 的元素子序列的值为 [-1, -2]\n",
+    "## 修改从第 0 到第 2 的元素子列表的值为 [-1, -2]\n",
     "l[0:2] = [-1, -2]\n",
     "print(l)"
    ]
@@ -230,7 +230,7 @@
    "id": "political-astrology",
    "metadata": {},
    "source": [
-    "通过 `append` 函数可以实现向序列尾部添加新的元素。"
+    "通过 `append` 函数可以实现向列表尾部添加新的元素。"
    ]
   },
   {
@@ -270,7 +270,7 @@
    "id": "similar-delhi",
    "metadata": {},
    "source": [
-    "通过 `del` 关键字可以删除序列某个位置的元素。"
+    "通过 `del` 关键字可以删除列表某个位置的元素。"
    ]
   },
   {
@@ -289,10 +289,10 @@
     }
    ],
    "source": [
-    "## 删除序列 首个 元素\n",
+    "## 删除列表 首个 元素\n",
     "del l[0]\n",
     "print(l)\n",
-    "## 删除序列 最后一个 元素\n",
+    "## 删除列表 最后一个 元素\n",
     "del l[-1]\n",
     "print(l)"
    ]
@@ -310,7 +310,7 @@
    "id": "correct-coalition",
    "metadata": {},
    "source": [
-    "在熟悉了序列的增删查找功能后，我们就可以尝试以此为基础搭建我们的学生成绩管理系统。"
+    "在熟悉了列表的增删查找功能后，我们就可以尝试以此为基础搭建我们的学生成绩管理系统。"
    ]
   },
   {
@@ -342,12 +342,12 @@
    "source": [
     "## Task 1 建立学生信息管理系统\n",
     "\n",
-    "## 首先建立一个 “名字” 序列记录哪个学生在序列的哪个位置。\n",
+    "## 首先建立一个 “名字” 列表记录哪个学生在列表的哪个位置。\n",
     "names = ['XiaoHu', 'XiaoMing', 'XiaoWei']\n",
     "\n",
-    "## 根据名字序列的位置分别建立 “语文成绩” “数学成绩序列” 序列。\n",
-    "math_scores = [65, 80, 95]\n",
-    "language_scores = [55, 92, 98]"
+    "## 根据名字列表的位置分别建立 “语文成绩” “数学成绩列表” 列表。\n",
+    "Math_scores = [65, 80, 95]\n",
+    "Chinese_scores = [55, 92, 98]"
    ]
   },
   {
@@ -361,35 +361,35 @@
     "\n",
     "## 首先找到 \"XiaoHu\" 在哪个位置，更新该位置的成绩\n",
     "## 通过 for-in 循环遍历名字元素\n",
-    "position = -1\n",
+    "position = None\n",
     "count = 0\n",
     "for name in names:\n",
-    "    ## 找到 XiaoHu 在序列中的位置\n",
+    "    ## 找到 XiaoHu 在列表中的位置\n",
     "    if name == \"XiaoHu\":\n",
     "        position = count\n",
     "    count = count + 1\n",
-    "## 根据 XiaoHu 在序列中的位置更新成绩\n",
-    "math_scores[position] = 95\n",
-    "language_scores[position] = 85\n",
+    "## 根据 XiaoHu 在列表中的位置更新成绩\n",
+    "Math_scores[position] = 95\n",
+    "Chinese_scores[position] = 85\n",
     "\n",
     "## 以同样方法更新 XiaoMing 与 XiaoWei 的成绩\n",
-    "position = -1\n",
+    "position = None\n",
     "count = 0\n",
     "for name in names:\n",
     "    if name == \"XiaoMing\":\n",
     "        position = count\n",
     "    count = count + 1\n",
-    "math_scores[position] = 75\n",
-    "language_scores[position] = 71\n",
+    "Math_scores[position] = 75\n",
+    "Chinese_scores[position] = 71\n",
     "\n",
-    "position = -1\n",
+    "position = None\n",
     "count = 0\n",
     "for name in names:\n",
     "    if name == \"XiaoWei\":\n",
     "        position = count\n",
     "    count = count + 1\n",
-    "math_scores[position] = 92\n",
-    "language_scores[position] = 93"
+    "Math_scores[position] = 92\n",
+    "Chinese_scores[position] = 93"
    ]
   },
   {
@@ -410,8 +410,8 @@
    ],
    "source": [
     "print(names)\n",
-    "print(math_scores)\n",
-    "print(language_scores)"
+    "print(Math_scores)\n",
+    "print(Chinese_scores)"
    ]
   },
   {
@@ -425,17 +425,17 @@
     "\n",
     "## 首先找到 \"XiaoMing\" 在哪个位置\n",
     "## 通过 for-in 循环遍历名字元素\n",
-    "position = -1\n",
+    "position = None\n",
     "count = 0\n",
     "for name in names:\n",
-    "    ## 找到 XiaoMing 在序列中的位置\n",
+    "    ## 找到 XiaoMing 在列表中的位置\n",
     "    if name == \"XiaoMing\":\n",
     "        position = count\n",
     "    count = count + 1\n",
-    "## 根据 XiaoMing 在序列中的位置删除\n",
+    "## 根据 XiaoMing 在列表中的位置删除\n",
     "del names[position]\n",
-    "del math_scores[position]\n",
-    "del language_scores[position]"
+    "del Math_scores[position]\n",
+    "del Chinese_scores[position]"
    ]
   },
   {
@@ -456,13 +456,13 @@
    ],
    "source": [
     "print(names)\n",
-    "print(math_scores)\n",
-    "print(language_scores)"
+    "print(Math_scores)\n",
+    "print(Chinese_scores)"
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": 13,
+   "execution_count": 14,
    "id": "homeless-bangladesh",
    "metadata": {},
    "outputs": [],
@@ -470,13 +470,13 @@
     "## Task 4 录入 Cryin 的信息\n",
     "\n",
     "names.append('Cryin')\n",
-    "math_scores.append(87)\n",
-    "language_scores.append(88)"
+    "Math_scores.append(87)\n",
+    "Chinese_scores.append(88)"
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": 14,
+   "execution_count": 13,
    "id": "european-encounter",
    "metadata": {},
    "outputs": [
@@ -484,16 +484,16 @@
      "name": "stdout",
      "output_type": "stream",
      "text": [
-      "['XiaoHu', 'XiaoWei', 'Cryin']\n",
-      "[95, 92, 87]\n",
-      "[85, 93, 88]\n"
+      "['XiaoHu', 'XiaoWei']\n",
+      "[95, 92]\n",
+      "[85, 93]\n"
      ]
     }
    ],
    "source": [
     "print(names)\n",
-    "print(math_scores)\n",
-    "print(language_scores)"
+    "print(Math_scores)\n",
+    "print(Chinese_scores)"
    ]
   },
   {
@@ -501,7 +501,7 @@
    "id": "confident-utility",
    "metadata": {},
    "source": [
-    "以上我们就初步实现了学生成绩管理系统，并实现了用户的一些简单需求。可以发现序列的增删改操作相对轻松，但最困难的部分是需要遍历整个序列寻找元素在序列中的位置，这种困难是由序列在计算机中的存储形式决定的。后面我们介绍的数据结构 “字典” 可以用来解决这个问题。"
+    "以上我们就初步实现了学生成绩管理系统，并实现了用户的一些简单需求。可以发现列表的增删改操作相对轻松，但最困难的部分是需要遍历整个列表寻找元素在列表中的位置，这种困难是由列表在计算机中的存储形式决定的。后面我们介绍的数据结构 “字典” 可以用来解决这个问题。"
    ]
   },
   {
@@ -660,9 +660,9 @@
    "metadata": {},
    "source": [
     "字典支持以下操作：\n",
-    "- 增：通过关键字 `[ ]` 可以向序列内增加元素\n",
-    "- 删：通过关键字 `del` 可以删除序列内元素\n",
-    "- 查：通过关键字 `[ ]` 可以查找序列某个位置元素\n",
+    "- 增：通过关键字 `[ ]` 可以向列表内增加元素\n",
+    "- 删：通过关键字 `del` 可以删除列表内元素\n",
+    "- 查：通过关键字 `[ ]` 可以查找列表某个位置元素\n",
     "- 改：通过赋值符号 `=` 可以修改某个位置的元素\n",
     "\n",
     "字典的优点是：\n",
@@ -840,18 +840,18 @@
    "source": [
     "## Task 1 建立学生信息管理系统\n",
     "\n",
-    "math_scores = {}\n",
-    "math_scores['XiaoHu'] = 65\n",
-    "math_scores['XiaoMing'] = 80\n",
-    "math_scores['XiaoWei'] = 95\n",
+    "Math_scores = {}\n",
+    "Math_scores['XiaoHu'] = 65\n",
+    "Math_scores['XiaoMing'] = 80\n",
+    "Math_scores['XiaoWei'] = 95\n",
     "\n",
-    "language_scores = {}\n",
-    "language_scores['XiaoHu'] = 55\n",
-    "language_scores['XiaoMing'] = 92\n",
-    "language_scores['XiaoWei'] = 98\n",
+    "Chinese_scores = {}\n",
+    "Chinese_scores['XiaoHu'] = 55\n",
+    "Chinese_scores['XiaoMing'] = 92\n",
+    "Chinese_scores['XiaoWei'] = 98\n",
     "\n",
-    "print(math_scores)\n",
-    "print(language_scores)"
+    "print(Math_scores)\n",
+    "print(Chinese_scores)"
    ]
   },
   {
@@ -872,17 +872,17 @@
    "source": [
     "## Task 2 根据本次期末考试的成绩更新系统\n",
     "\n",
-    "math_scores['XiaoHu'] = 95\n",
-    "math_scores['XiaoMing'] = 75\n",
-    "math_scores['XiaoWei'] = 92\n",
+    "Math_scores['XiaoHu'] = 95\n",
+    "Math_scores['XiaoMing'] = 75\n",
+    "Math_scores['XiaoWei'] = 92\n",
     "\n",
-    "language_scores = {}\n",
-    "language_scores['XiaoHu'] = 85\n",
-    "language_scores['XiaoMing'] = 71\n",
-    "language_scores['XiaoWei'] = 93\n",
+    "Chinese_scores = {}\n",
+    "Chinese_scores['XiaoHu'] = 85\n",
+    "Chinese_scores['XiaoMing'] = 71\n",
+    "Chinese_scores['XiaoWei'] = 93\n",
     "\n",
-    "print(math_scores)\n",
-    "print(language_scores)"
+    "print(Math_scores)\n",
+    "print(Chinese_scores)"
    ]
   },
   {
@@ -903,11 +903,11 @@
    "source": [
     "## Task 3 删除 XiaoMing 的信息\n",
     "\n",
-    "del math_scores['XiaoMing']\n",
-    "del language_scores['XiaoMing']\n",
+    "del Math_scores['XiaoMing']\n",
+    "del Chinese_scores['XiaoMing']\n",
     "\n",
-    "print(math_scores)\n",
-    "print(language_scores)"
+    "print(Math_scores)\n",
+    "print(Chinese_scores)"
    ]
   },
   {
@@ -928,11 +928,11 @@
    "source": [
     "## Task 4 录入 Cryin 的信息\n",
     "\n",
-    "math_scores['Cryin'] = 87\n",
-    "language_scores['Cryin'] = 88\n",
+    "Math_scores['Cryin'] = 87\n",
+    "Chinese_scores['Cryin'] = 88\n",
     "\n",
-    "print(math_scores)\n",
-    "print(language_scores)"
+    "print(Math_scores)\n",
+    "print(Chinese_scores)"
    ]
   },
   {
@@ -1160,7 +1160,7 @@
     }
    ],
    "source": [
-    "## 集合亦或\n",
+    "## 集合异或，即不属于交集的部分\n",
     "print(s ^ s2)"
    ]
   },
@@ -1177,7 +1177,7 @@
    "id": "static-framework",
    "metadata": {},
    "source": [
-    "### 1.2.5.1 序列练习"
+    "### 1.2.5.1 列表练习"
    ]
   },
   {
@@ -1186,7 +1186,7 @@
    "metadata": {},
    "source": [
     "<blockquote>\n",
-    "给定两个大小分别为 m 和 n 的升序（从小到大）序列 nums1 和 nums2。请你找出并返回这两个升序序列的 中位数 。\n",
+    "给定两个大小分别为 m 和 n 的升序（从小到大）列表 nums1 和 nums2。请你找出并返回这两个升序列表的 中位数 。\n",
     "\n",
     "例子：\n",
     "    \n",
@@ -1201,7 +1201,7 @@
    "id": "instrumental-melbourne",
    "metadata": {},
    "source": [
-    "找到两个序列的中位数的思路分两步，首先合并两个升序序列为一个升序序列，然后找到升序序列中中间的数即为中位数。"
+    "找到两个列表的中位数的思路分两步，首先合并两个升序列表为一个升序列表，然后找到升序列表中中间的数即为中位数。"
    ]
   },
   {
@@ -1209,7 +1209,7 @@
    "id": "express-insulin",
    "metadata": {},
    "source": [
-    "合并两个升序序列的思路很简单，因为两个序列都是升序，所以只需要判断两个序列首个元素的大小，将最小的依次放入一个新的数组中。如果其中一个数组空了，说明另一个数组中的所有元素都比之前的大，将它们合并到新数组的尾部即可。"
+    "合并两个升序列表的思路很简单，因为两个列表都是升序，所以只需要判断两个列表首个元素的大小，将最小的依次放入一个新的数组中。如果其中一个数组空了，说明另一个数组中的所有元素都比之前的大，将它们合并到新数组的尾部即可。"
    ]
   },
   {
@@ -1219,22 +1219,22 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "## 定义合并两个升序序列的函数\n",
+    "## 定义合并两个升序列表的函数\n",
     "def merge(nums1, nums2):\n",
     "    result = []\n",
-    "    ## 如果两个序列都不是空的，依次比较首个元素大小\n",
+    "    ## 如果两个列表都不是空的，依次比较首个元素大小\n",
     "    while len(nums1) > 0 and len(nums2) > 0:\n",
-    "        ## 如果第一个序列首个元素更小\n",
+    "        ## 如果第一个列表首个元素更小\n",
     "        if nums1[0] < nums2[0]:\n",
-    "            ## 将 nums1 序列的首个元素放入 result 序列\n",
+    "            ## 将 nums1 列表的首个元素放入 result 列表\n",
     "            result.append(nums1[0])\n",
     "            nums1 = nums1[1:]\n",
-    "        ## 如果第 nums2 序列首个元素更小\n",
+    "        ## 如果第 nums2 列表首个元素更小\n",
     "        else:\n",
-    "            ## 将 nums2 序列的首个元素放入 result 序列\n",
+    "            ## 将 nums2 列表的首个元素放入 result 列表\n",
     "            result.append(nums2[0])\n",
     "            nums2 = nums2[1:]\n",
-    "    ## 如果某个序列空了，将非空的数组合并到 result 尾部\n",
+    "    ## 如果某个列表空了，将非空的数组合并到 result 尾部\n",
     "    result = result + nums1\n",
     "    result = result + nums2\n",
     "    return result"
@@ -1247,13 +1247,13 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "## 在合并后的序列中寻找中位数\n",
+    "## 在合并后的列表中寻找中位数\n",
     "def find_medium(nums):\n",
     "    half = len(nums) // 2\n",
-    "    ## 如果序列长度为偶数，则取中间两个数的平均值\n",
+    "    ## 如果列表长度为偶数，则取中间两个数的平均值\n",
     "    if len(nums) % 2 == 0:\n",
     "        return (nums[half - 1] + nums[half]) / 2\n",
-    "    ## 如果序列长度为奇数，则取最中间数\n",
+    "    ## 如果列表长度为奇数，则取最中间数\n",
     "    else:\n",
     "        return nums[half]"
    ]
@@ -1436,7 +1436,7 @@
    "id": "brief-oakland",
    "metadata": {},
    "source": [
-    "那么在上述程序中，输入序列的大小为 4，在最坏情况下 twosum 函数中的两个 for-in 循环一共执行 16 次 check_sum 操作，因此该算法的复杂度是$O(n^2)$。下面我们用 字典 优化代码复杂度为 $O(n)$，思路是遍历一次序列并将遍历过的元素值存储到字典中，若有字典中的元素值与序列中的元素值求和为target，则返回这两个值。"
+    "那么在上述程序中，输入列表的大小为 4，在最坏情况下 twosum 函数中的两个 for-in 循环一共执行 16 次 check_sum 操作，因此该算法的复杂度是$O(n^2)$。下面我们用 字典 优化代码复杂度为 $O(n)$，思路是遍历一次列表并将遍历过的元素值存储到字典中，若有字典中的元素值与列表中的元素值求和为target，则返回这两个值。"
    ]
   },
   {
@@ -1477,11 +1477,8 @@
   }
  ],
  "metadata": {
-  "interpreter": {
-   "hash": "b658b93575a16dafdf00f5313d36bbc5ac0ec49ea379e64c9fa6db2ffc1a77f9"
-  },
   "kernelspec": {
-   "display_name": "Python 3.9.2 64-bit",
+   "display_name": "Python 3.7.1 ('DataScience')",
    "language": "python",
    "name": "python3"
   },
@@ -1495,7 +1492,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.9.2"
+   "version": "3.7.1"
   },
   "notify_time": "10",
   "toc": {
@@ -1515,6 +1512,11 @@
    },
    "toc_section_display": true,
    "toc_window_display": true
+  },
+  "vscode": {
+   "interpreter": {
+    "hash": "4951620600495571d210fcc70149573e34741e5378bdea11097277e6fa3349d5"
+   }
   }
  },
  "nbformat": 4,
diff --git a/3. Python 面向对象编程.ipynb b/3. Python 面向对象编程.ipynb
index 70b8a8b..e00815f 100644
--- a/3. Python 面向对象编程.ipynb	
+++ b/3. Python 面向对象编程.ipynb	
@@ -198,7 +198,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 1,
+   "execution_count": null,
    "id": "whole-translation",
    "metadata": {},
    "outputs": [],
@@ -218,19 +218,10 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 2,
+   "execution_count": null,
    "id": "marked-hello",
    "metadata": {},
-   "outputs": [
-    {
-     "name": "stdout",
-     "output_type": "stream",
-     "text": [
-      "<class '__main__.student'>\n",
-      "<class '__main__.student'>\n"
-     ]
-    }
-   ],
+   "outputs": [],
    "source": [
     "## 使用 类的名字 student 与 括号() 可以创建类的对象 xiaohu\n",
     "xiaohu = student()\n",
@@ -253,12 +244,12 @@
    "id": "injured-difference",
    "metadata": {},
    "source": [
-    "我们提到类与对象都有包含一组属性与方法，在 Python 中类的变量用于表示类的属性。`student` 表示学生类，在我们的系统中我们只关注学生的姓名、数学成绩和语文成绩而不考虑其他，分别用类变量 `name`, `math_score`, `language_score` 表示。这体现了面向对象编程的”抽象性“。"
+    "我们提到类与对象都有包含一组属性与方法，在 Python 中类的变量用于表示类的属性。`student` 表示学生类，在我们的系统中我们只关注学生的姓名、数学成绩和语文成绩而不考虑其他，分别用类变量 `name`, `Math_score`, `Chinese_score` 表示。这体现了面向对象编程的”抽象性“。"
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": 3,
+   "execution_count": null,
    "id": "severe-reset",
    "metadata": {},
    "outputs": [],
@@ -266,9 +257,9 @@
     "## 创建一个 student 类\n",
     "class student():\n",
     "    ## 类的内部定义三个内部变量，并定义他们的初始值\n",
-    "    name = 'Undifined'\n",
-    "    math_score = -1\n",
-    "    language_score = -1"
+    "    name = 'Undefined'\n",
+    "    Math_score = None\n",
+    "    Chinese_score = None"
    ]
   },
   {
@@ -281,27 +272,17 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 4,
+   "execution_count": null,
    "id": "manual-montreal",
    "metadata": {},
-   "outputs": [
-    {
-     "name": "stdout",
-     "output_type": "stream",
-     "text": [
-      "Undifined\n",
-      "-1\n",
-      "-1\n"
-     ]
-    }
-   ],
+   "outputs": [],
    "source": [
     "## 使用 类的名字 student 与 括号() 可以创建类的对象 xiaohu\n",
     "xiaohu = student()\n",
-    "## 使用 . 符号引用对象xiaohu的变量name、math_score、language_score\n",
+    "## 使用 . 符号引用对象xiaohu的变量name、Math_score、Chinese_score\n",
     "print(xiaohu.name)\n",
-    "print(xiaohu.math_score)\n",
-    "print(xiaohu.language_score)"
+    "print(xiaohu.Math_score)\n",
+    "print(xiaohu.Chinese_score)"
    ]
   },
   {
@@ -314,29 +295,19 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 5,
+   "execution_count": null,
    "id": "black-pakistan",
    "metadata": {},
-   "outputs": [
-    {
-     "name": "stdout",
-     "output_type": "stream",
-     "text": [
-      "XiaoHu\n",
-      "65\n",
-      "55\n"
-     ]
-    }
-   ],
+   "outputs": [],
    "source": [
     "## 通过赋值符号改变对象内变量的值\n",
     "xiaohu.name = 'XiaoHu'\n",
-    "xiaohu.math_score = 65\n",
-    "xiaohu.language_score = 55\n",
+    "xiaohu.Math_score = 65\n",
+    "xiaohu.Chinese_score = 55\n",
     "\n",
     "print(xiaohu.name)\n",
-    "print(xiaohu.math_score)\n",
-    "print(xiaohu.language_score)"
+    "print(xiaohu.Math_score)\n",
+    "print(xiaohu.Chinese_score)"
    ]
   },
   {
@@ -352,19 +323,10 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 6,
+   "execution_count": null,
    "id": "south-tongue",
    "metadata": {},
-   "outputs": [
-    {
-     "name": "stdout",
-     "output_type": "stream",
-     "text": [
-      "XiaoMing\n",
-      "XiaoHu\n"
-     ]
-    }
-   ],
+   "outputs": [],
    "source": [
     "## 更改对象变量只影响该对象的属性。\n",
     "xiaoming = student()\n",
@@ -376,19 +338,10 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 7,
+   "execution_count": null,
    "id": "loose-albuquerque",
    "metadata": {},
-   "outputs": [
-    {
-     "name": "stdout",
-     "output_type": "stream",
-     "text": [
-      "Undifined\n",
-      "Change Name\n"
-     ]
-    }
-   ],
+   "outputs": [],
    "source": [
     "## 更改类变量会影响所有后续由该类创建对象的属性。\n",
     "xiaoming = student()\n",
@@ -420,7 +373,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 8,
+   "execution_count": null,
    "id": "heavy-jewel",
    "metadata": {},
    "outputs": [],
@@ -430,25 +383,17 @@
     "    def print_name(self,):\n",
     "        print(self.name)\n",
     "        \n",
-    "    name = 'Undifined'\n",
-    "    math_score = -1\n",
-    "    language_score = -1"
+    "    name = 'Undefined'\n",
+    "    Math_score = None\n",
+    "    Chinese_score = None"
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": 9,
+   "execution_count": null,
    "id": "occasional-paint",
    "metadata": {},
-   "outputs": [
-    {
-     "name": "stdout",
-     "output_type": "stream",
-     "text": [
-      "Xiaohu\n"
-     ]
-    }
-   ],
+   "outputs": [],
    "source": [
     "xiaohu = student()\n",
     "xiaohu.name = 'Xiaohu'\n",
@@ -475,7 +420,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 10,
+   "execution_count": null,
    "id": "colonial-craps",
    "metadata": {},
    "outputs": [],
@@ -483,41 +428,34 @@
     "class student():\n",
     "    ## 定义一个修改对象数据值的函数\n",
     "    def change_score(self, course_name, score):\n",
-    "        if course_name == 'math':\n",
-    "            self.math_score = score\n",
-    "        if course_name == 'language':\n",
-    "            self.language_score = score\n",
-    "        ## 如果输入的 course_name 不是 math 或者 language，则输出错误信息\n",
-    "        print(course_name, \" course is still not in current system\")\n",
+    "        if course_name == 'Math':\n",
+    "            self.Math_score = score\n",
+    "        elif course_name == 'Chinese':\n",
+    "            self.Chinese_score = score\n",
+    "        ## 如果输入的 course_name 不是 Math 或者 Chinese，则输出错误信息\n",
+    "        else:\n",
+    "            print(course_name, \" course is still not in current system\")\n",
     "    \n",
     "    def print_name(self,):\n",
     "        print(self.name)\n",
     "        \n",
-    "    name = 'Undifined'\n",
-    "    math_score = -1\n",
-    "    language_score = -1"
+    "    name = 'Undefined'\n",
+    "    Math_score = None\n",
+    "    Chinese_score = None"
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": 11,
+   "execution_count": null,
    "id": "split-burner",
    "metadata": {},
-   "outputs": [
-    {
-     "name": "stdout",
-     "output_type": "stream",
-     "text": [
-      "language  course is still not in current system\n"
-     ]
-    }
-   ],
+   "outputs": [],
    "source": [
     "xiaohu = student()\n",
     "xiaohu.name = 'Xiaohu'\n",
-    "xiaohu.change_score('math', 65)\n",
-    "xiaohu.change_score('language',55)\n",
-    "xiaohu.change_score('physics',48)"
+    "xiaohu.change_score('Math', 65)\n",
+    "xiaohu.change_score('Chinese',55)\n",
+    "xiaohu.change_score('Physics',48)"
    ]
   },
   {
@@ -544,8 +482,8 @@
     "在之前的代码中，我们采用赋值符号来为对象产生初始值：\n",
     "\n",
     "    xiaohu.name = 'XiaoHu'\n",
-    "    xiaohu.math_score = 65\n",
-    "    xiaohu.language_score = 55\n",
+    "    xiaohu.Math_score = 65\n",
+    "    xiaohu.Chinese_score = 55\n",
     "    \n",
     "然而这种方式或许有些麻烦，其实 Python 类中有一种 `__init__` 方法专门用于初始化对象。这个方法在通过类创建对象时被自动调用，并按照你的想法初始化该对象。下面我们通过 `__init__` 方法重新定义 student 类：\n",
     "\n"
@@ -560,26 +498,26 @@
    "source": [
     "class student():\n",
     "    ## 定义 __init__ 方法，通过该方法的参数输入初始值，在该方法内部为变量赋值\n",
-    "    def __init__(self, name, math_score, language_score):\n",
+    "    def __init__(self, name, Math_score, Chinese_score):\n",
     "        self.name = name\n",
-    "        self.math_score = math_score\n",
-    "        self.language_score = language_score\n",
+    "        self.Math_score = Math_score\n",
+    "        self.Chinese_score = Chinese_score\n",
     "    \n",
     "    def change_score(self, course_name, score):\n",
-    "        if course_name == 'math':\n",
-    "            self.math_score = score\n",
-    "        elif course_name == 'language':\n",
-    "            self.language_score = score\n",
-    "        ## 如果输入的 course_name 不是 math 或者 language，则输出错误信息\n",
+    "        if course_name == 'Math':\n",
+    "            self.Math_score = score\n",
+    "        elif course_name == 'Chinese':\n",
+    "            self.Chinese_score = score\n",
+    "        ## 如果输入的 course_name 不是 Math 或者 Chinese，则输出错误信息\n",
     "        else:\n",
     "            print(course_name, \" course is still not in current system\")\n",
     "    \n",
     "    def print_name(self,):\n",
     "        print(self.name)\n",
     "    \n",
-    "    name = 'Undifined'\n",
-    "    math_score = -1\n",
-    "    language_score = -1"
+    "    name = 'Undefined'\n",
+    "    Math_score = None\n",
+    "    Chinese_score = None"
    ]
   },
   {
@@ -1078,29 +1016,29 @@
    "outputs": [],
    "source": [
     "class student():\n",
-    "    def __init__(self, name, math_score, language_score):\n",
+    "    def __init__(self, name, Math_score, Chinese_score):\n",
     "        self.name = name\n",
-    "        self.math_score = math_score\n",
-    "        self.language_score = language_score\n",
+    "        self.Math_score = Math_score\n",
+    "        self.Chinese_score = Chinese_score\n",
     "    \n",
     "    ## repr 函数用于定义对象被输出时的输出结果\n",
     "    def __repr__(self):\n",
-    "        return str((self.name, self.math_score, self.language_score))\n",
+    "        return str((self.name, self.Math_score, self.Chinese_score))\n",
     "    \n",
     "    def change_score(self, course_name, score):\n",
-    "        if course_name == 'math':\n",
-    "            self.math_score = score\n",
-    "        elif course_name == 'language':\n",
-    "            self.language_score = score\n",
+    "        if course_name == 'Math':\n",
+    "            self.Math_score = score\n",
+    "        elif course_name == 'Chinese':\n",
+    "            self.Chinese_score = score\n",
     "        else:\n",
     "            print(course_name, \" course is still not in current system\")\n",
     "    \n",
     "    def print_name(self,):\n",
     "        print(self.name)\n",
     "    \n",
-    "    name = 'Undifined'\n",
-    "    math_score = -1\n",
-    "    language_score = -1"
+    "    name = 'Undefined'\n",
+    "    Math_score = None\n",
+    "    Chinese_score = None"
    ]
   },
   {
@@ -1137,13 +1075,13 @@
     "print(ab)\n",
     "\n",
     "## Task2\n",
-    "ab['XiaoHu'].change_score('math', 95)\n",
-    "ab['XiaoMing'].change_score('math', 75)\n",
-    "ab['XiaoWei'].change_score('math', 92)\n",
+    "ab['XiaoHu'].change_score('Math', 95)\n",
+    "ab['XiaoMing'].change_score('Math', 75)\n",
+    "ab['XiaoWei'].change_score('Math', 92)\n",
     "\n",
-    "ab['XiaoHu'].change_score('language', 85)\n",
-    "ab['XiaoMing'].change_score('language', 71)\n",
-    "ab['XiaoWei'].change_score('language', 93)\n",
+    "ab['XiaoHu'].change_score('Chinese', 85)\n",
+    "ab['XiaoMing'].change_score('Chinese', 71)\n",
+    "ab['XiaoWei'].change_score('Chinese', 93)\n",
     "print(ab)\n",
     "\n",
     "## Task3\n",
@@ -1157,11 +1095,8 @@
   }
  ],
  "metadata": {
-  "interpreter": {
-   "hash": "6e6b1a68f12b475eafe78cfc17c6f5d94c7a04c458bc4083bc2db350380231c7"
-  },
   "kernelspec": {
-   "display_name": "Python 3",
+   "display_name": "Python 3.7.1 ('DataScience')",
    "language": "python",
    "name": "python3"
   },
@@ -1175,7 +1110,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.9.2"
+   "version": "3.7.1"
   },
   "toc": {
    "base_numbering": 1,
@@ -1194,6 +1129,11 @@
    },
    "toc_section_display": true,
    "toc_window_display": true
+  },
+  "vscode": {
+   "interpreter": {
+    "hash": "4951620600495571d210fcc70149573e34741e5378bdea11097277e6fa3349d5"
+   }
   }
  },
  "nbformat": 4,
diff --git a/4. Python 文件与模块.ipynb b/4. Python 文件与模块.ipynb
index 6243267..e15b10c 100644
--- a/4. Python 文件与模块.ipynb	
+++ b/4. Python 文件与模块.ipynb	
@@ -45,11 +45,33 @@
    "id": "508c28c5",
    "metadata": {},
    "source": [
-    "> 为了测试 python 中的文件操作，我们先通过命令行在当前目录保存一个内容为 “hello world!” 的 test.txt 文件。\n",
+    "> 为了测试 Python 中的文件操作，我们先通过命令行在当前目录保存一个内容为 “hello world!” 的 test.txt 文件。\n",
     "\n",
     "<img style=\"float: center;\" src=\"./src/fig41.png\" width=\"50%\"> "
    ]
   },
+  {
+   "cell_type": "markdown",
+   "id": "9acf44f7",
+   "metadata": {},
+   "source": [
+    "> 或者通过以下代码来生成 `test.txt` 文件"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 6,
+   "id": "161166fc",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "file = open('test.txt', 'w')\n",
+    "file.write(\"\"\"Hello world!\n",
+    "Hello Python!!\n",
+    "Hello smart way!!!\"\"\")\n",
+    "file.close()"
+   ]
+  },
   {
    "cell_type": "markdown",
    "id": "fd7d8214",
@@ -67,7 +89,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 1,
+   "execution_count": 7,
    "id": "85581df5",
    "metadata": {},
    "outputs": [
@@ -119,7 +141,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 2,
+   "execution_count": 8,
    "id": "c42d7de4",
    "metadata": {},
    "outputs": [
@@ -141,7 +163,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 3,
+   "execution_count": 9,
    "id": "0604c0d2",
    "metadata": {},
    "outputs": [
@@ -171,7 +193,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 4,
+   "execution_count": 10,
    "id": "7d180532",
    "metadata": {},
    "outputs": [
@@ -203,7 +225,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 5,
+   "execution_count": 11,
    "id": "8388fe2d",
    "metadata": {},
    "outputs": [],
@@ -236,7 +258,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 6,
+   "execution_count": 12,
    "id": "f3352cfd",
    "metadata": {},
    "outputs": [],
@@ -293,6 +315,49 @@
     "<img style=\"float: center;\" src=\"./src/fig44.png\" width=\"50%\"> "
    ]
   },
+  {
+   "cell_type": "markdown",
+   "id": "575e38db",
+   "metadata": {},
+   "source": [
+    "> 为了接下来的模块引入更方便，我们也可以使用下面的代码来直接在当前目录生成 `student.py` 文件。"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 2,
+   "id": "bc4a2658",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "file = open('student.py', 'w',encoding=\"utf-8\")\n",
+    "file.write(\"\"\"class student():\n",
+    "    def __init__(self, name, Math_score, Chinese_score):\n",
+    "        self.name = name\n",
+    "        self.Math_score = Math_score\n",
+    "        self.Chinese_score = Chinese_score\n",
+    "    \n",
+    "    ## repr 函数用于定义对象被输出时的输出结果\n",
+    "    def __repr__(self):\n",
+    "        return str((self.name, self.Math_score, self.Chinese_score))\n",
+    "    \n",
+    "    def change_score(self, course_name, score):\n",
+    "        if course_name == 'Math':\n",
+    "            self.Math_score = score\n",
+    "        elif course_name == 'Chinese':\n",
+    "            self.Chinese_score = score\n",
+    "        else:\n",
+    "            print(course_name, \" course is still not in current system\")\n",
+    "    \n",
+    "    def print_name(self,):\n",
+    "        print(self.name)\n",
+    "    \n",
+    "    name = 'Undefined'\n",
+    "    Math_score = None\n",
+    "    Chinese_score = None\"\"\")\n",
+    "file.close()"
+   ]
+  },
   {
    "cell_type": "markdown",
    "id": "ef0e6af7",
@@ -303,7 +368,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 7,
+   "execution_count": 3,
    "id": "8de02c29",
    "metadata": {},
    "outputs": [],
@@ -313,7 +378,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 8,
+   "execution_count": 4,
    "id": "4c9f7a60",
    "metadata": {},
    "outputs": [
@@ -348,7 +413,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 9,
+   "execution_count": 16,
    "id": "abf9e578",
    "metadata": {},
    "outputs": [
@@ -378,7 +443,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 10,
+   "execution_count": 17,
    "id": "323741ef",
    "metadata": {},
    "outputs": [
@@ -393,12 +458,12 @@
    "source": [
     "import math\n",
     "## 通过 math.log 计算数值的对数\n",
-    "print(math.log(xiaohu.math_score))"
+    "print(math.log(xiaohu.Math_score))"
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": 11,
+   "execution_count": 18,
    "id": "67f56bad",
    "metadata": {},
    "outputs": [
@@ -406,7 +471,7 @@
      "name": "stdout",
      "output_type": "stream",
      "text": [
-      "Thu Jul  1 09:51:16 2021\n"
+      "Tue Jul 12 18:44:42 2022\n"
      ]
     }
    ],
@@ -456,7 +521,7 @@
    "id": "f0673d08",
    "metadata": {},
    "source": [
-    "### 1.4.3.2 Python 之蝉"
+    "### 1.4.3.2 Python 之禅"
    ]
   },
   {
@@ -517,11 +582,8 @@
   }
  ],
  "metadata": {
-  "interpreter": {
-   "hash": "aee8b7b246df8f9039afb4144a1f6fd8d2ca17a180786b69acc140d282b71a49"
-  },
   "kernelspec": {
-   "display_name": "Python 3",
+   "display_name": "Python 3.7.1 ('DataScience')",
    "language": "python",
    "name": "python3"
   },
@@ -535,7 +597,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.9.2"
+   "version": "3.7.1"
   },
   "toc": {
    "base_numbering": 1,
@@ -549,6 +611,11 @@
    "toc_position": {},
    "toc_section_display": true,
    "toc_window_display": true
+  },
+  "vscode": {
+   "interpreter": {
+    "hash": "4951620600495571d210fcc70149573e34741e5378bdea11097277e6fa3349d5"
+   }
   }
  },
  "nbformat": 4,