diff --git a/codes/python/chapter_tree/avl_tree.py b/codes/python/chapter_tree/avl_tree.py
index 04218e46a..83929981d 100644
--- a/codes/python/chapter_tree/avl_tree.py
+++ b/codes/python/chapter_tree/avl_tree.py
@@ -5,30 +5,28 @@ Author: a16su (lpluls001@gmail.com)
 """
 
 import sys, os.path as osp
-import typing
-
 sys.path.append(osp.dirname(osp.dirname(osp.abspath(__file__))))
 from include import *
 
 
 class AVLTree:
-    def __init__(self, root: typing.Optional[TreeNode] = None):
+    def __init__(self, root: Optional[TreeNode] = None):
         self.root = root
 
     """ 获取结点高度 """
-    def height(self, node: typing.Optional[TreeNode]) -> int:
+    def height(self, node: Optional[TreeNode]) -> int:
         # 空结点高度为 -1 ，叶结点高度为 0
         if node is not None:
             return node.height
         return -1
 
     """ 更新结点高度 """
-    def __update_height(self, node: TreeNode):
+    def __update_height(self, node: Optional[TreeNode]):
         # 结点高度等于最高子树高度 + 1
         node.height = max([self.height(node.left), self.height(node.right)]) + 1
 
     """ 获取平衡因子 """
-    def balance_factor(self, node: TreeNode) -> int:
+    def balance_factor(self, node: Optional[TreeNode]) -> int:
         # 空结点平衡因子为 0
         if node is None:
             return 0
@@ -36,7 +34,7 @@ class AVLTree:
         return self.height(node.left) - self.height(node.right)
 
     """ 右旋操作 """
-    def __right_rotate(self, node: TreeNode) -> TreeNode:
+    def __right_rotate(self, node: Optional[TreeNode]) -> TreeNode:
         child = node.left
         grand_child = child.right
         # 以 child 为原点，将 node 向右旋转
@@ -49,7 +47,7 @@ class AVLTree:
         return child
 
     """ 左旋操作 """
-    def __left_rotate(self, node: TreeNode) -> TreeNode:
+    def __left_rotate(self, node: Optional[TreeNode]) -> TreeNode:
         child = node.right
         grand_child = child.left
         # 以 child 为原点，将 node 向左旋转
@@ -62,7 +60,7 @@ class AVLTree:
         return child
 
     """ 执行旋转操作，使该子树重新恢复平衡 """
-    def __rotate(self, node: TreeNode) -> TreeNode:
+    def __rotate(self, node: Optional[TreeNode]) -> TreeNode:
         # 获取结点 node 的平衡因子
         balance_factor = self.balance_factor(node)
         # 左偏树
@@ -92,7 +90,7 @@ class AVLTree:
         return self.root
 
     """ 递归插入结点（辅助函数）"""
-    def __insert_helper(self, node: typing.Optional[TreeNode], val: int) -> TreeNode:
+    def __insert_helper(self, node: Optional[TreeNode], val: int) -> TreeNode:
         if node is None:
             return TreeNode(val)
         # 1. 查找插入位置，并插入结点
@@ -114,7 +112,7 @@ class AVLTree:
         return root
 
     """ 递归删除结点（辅助函数） """
-    def __remove_helper(self, node: typing.Optional[TreeNode], val: int) -> typing.Optional[TreeNode]:
+    def __remove_helper(self, node: Optional[TreeNode], val: int) -> Optional[TreeNode]:
         if node is None:
             return None
         # 1. 查找结点，并删除之
@@ -141,7 +139,7 @@ class AVLTree:
         return self.__rotate(node)
 
     """ 获取中序遍历中的下一个结点（仅适用于 root 有左子结点的情况） """
-    def __get_inorder_next(self, node: typing.Optional[TreeNode]) -> typing.Optional[TreeNode]:
+    def __get_inorder_next(self, node: Optional[TreeNode]) -> Optional[TreeNode]:
         if node is None:
             return None
         # 循环访问左子结点，直到叶结点时为最小结点，跳出
diff --git a/codes/python/chapter_tree/binary_search_tree.py b/codes/python/chapter_tree/binary_search_tree.py
index 7633b6288..2a8272761 100644
--- a/codes/python/chapter_tree/binary_search_tree.py
+++ b/codes/python/chapter_tree/binary_search_tree.py
@@ -5,20 +5,18 @@ Author: a16su (lpluls001@gmail.com)
 """
 
 import sys, os.path as osp
-import typing
-
 sys.path.append(osp.dirname(osp.dirname(osp.abspath(__file__))))
 from include import *
 
 
 """ 二叉搜索树 """
 class BinarySearchTree:
-    def __init__(self, nums: typing.List[int]) -> None:
+    def __init__(self, nums: List[int]) -> None:
         nums.sort()
         self.__root = self.build_tree(nums, 0, len(nums) - 1)
 
     """ 构建二叉搜索树 """
-    def build_tree(self, nums: typing.List[int], start_index: int, end_index: int) -> typing.Optional[TreeNode]:
+    def build_tree(self, nums: List[int], start_index: int, end_index: int) -> Optional[TreeNode]:
         if start_index > end_index:
             return None
 
@@ -31,11 +29,11 @@ class BinarySearchTree:
         return root
 
     @property
-    def root(self) -> typing.Optional[TreeNode]:
+    def root(self) -> Optional[TreeNode]:
         return self.__root
 
     """ 查找结点 """
-    def search(self, num: int) -> typing.Optional[TreeNode]:
+    def search(self, num: int) -> Optional[TreeNode]:
         cur = self.root
         # 循环查找，越过叶结点后跳出
         while cur is not None:
@@ -51,7 +49,7 @@ class BinarySearchTree:
         return cur
 
     """ 插入结点 """
-    def insert(self, num: int) -> typing.Optional[TreeNode]:
+    def insert(self, num: int) -> Optional[TreeNode]:
         root = self.root
         # 若树为空，直接提前返回
         if root is None:
@@ -81,7 +79,7 @@ class BinarySearchTree:
         return node
 
     """ 删除结点 """
-    def remove(self, num: int) -> typing.Optional[TreeNode]:
+    def remove(self, num: int) -> Optional[TreeNode]:
         root = self.root
         # 若树为空，直接提前返回
         if root is None:
@@ -126,7 +124,7 @@ class BinarySearchTree:
         return cur
 
     """ 获取中序遍历中的下一个结点（仅适用于 root 有左子结点的情况） """
-    def get_inorder_next(self, root: typing.Optional[TreeNode]) -> typing.Optional[TreeNode]:
+    def get_inorder_next(self, root: Optional[TreeNode]) -> Optional[TreeNode]:
         if root is None:
             return root
         # 循环访问左子结点，直到叶结点时为最小结点，跳出
diff --git a/codes/python/chapter_tree/binary_tree_bfs.py b/codes/python/chapter_tree/binary_tree_bfs.py
index 225a8bd6e..fb3e93059 100644
--- a/codes/python/chapter_tree/binary_tree_bfs.py
+++ b/codes/python/chapter_tree/binary_tree_bfs.py
@@ -5,14 +5,12 @@ Author: a16su (lpluls001@gmail.com)
 """
 
 import sys, os.path as osp
-import typing
-
 sys.path.append(osp.dirname(osp.dirname(osp.abspath(__file__))))
 from include import *
 
 
 """ 层序遍历 """
-def hier_order(root: TreeNode):
+def hier_order(root: Optional[TreeNode]):
     # 初始化队列，加入根结点
     queue = collections.deque()
     queue.append(root)
diff --git a/codes/python/chapter_tree/binary_tree_dfs.py b/codes/python/chapter_tree/binary_tree_dfs.py
index a1d46e697..b0efb14c8 100644
--- a/codes/python/chapter_tree/binary_tree_dfs.py
+++ b/codes/python/chapter_tree/binary_tree_dfs.py
@@ -5,8 +5,6 @@ Author: a16su (lpluls001@gmail.com)
 """
 
 import sys, os.path as osp
-import typing
-
 sys.path.append(osp.dirname(osp.dirname(osp.abspath(__file__))))
 from include import *
 
@@ -14,7 +12,7 @@ from include import *
 res = []
 
 """ 前序遍历 """
-def pre_order(root: typing.Optional[TreeNode]):
+def pre_order(root: Optional[TreeNode]):
     if root is None:
         return
     # 访问优先级：根结点 -> 左子树 -> 右子树
@@ -23,7 +21,7 @@ def pre_order(root: typing.Optional[TreeNode]):
     pre_order(root=root.right)
 
 """ 中序遍历 """
-def in_order(root: typing.Optional[TreeNode]):
+def in_order(root: Optional[TreeNode]):
     if root is None:
         return
     # 访问优先级：左子树 -> 根结点 -> 右子树
@@ -32,7 +30,7 @@ def in_order(root: typing.Optional[TreeNode]):
     in_order(root=root.right)
 
 """ 后序遍历 """
-def post_order(root: typing.Optional[TreeNode]):
+def post_order(root: Optional[TreeNode]):
     if root is None:
         return
     # 访问优先级：左子树 -> 右子树 -> 根结点
diff --git a/codes/python/include/__init__.py b/codes/python/include/__init__.py
index 31ed69ace..9d4e90bee 100644
--- a/codes/python/include/__init__.py
+++ b/codes/python/include/__init__.py
@@ -4,7 +4,7 @@ import queue
 import random
 import functools
 import collections
-from typing import List
+from typing import Optional, List, Dict, DefaultDict, OrderedDict, Set, Deque
 from .linked_list import ListNode, list_to_linked_list, linked_list_to_list, get_list_node
 from .binary_tree import TreeNode, list_to_tree, tree_to_list, get_tree_node
 from .print_util import print_matrix, print_linked_list, print_tree, print_dict
\ No newline at end of file
diff --git a/docs/chapter_tree/avl_tree.md b/docs/chapter_tree/avl_tree.md
index 8fc2313c7..9944f29e8 100644
--- a/docs/chapter_tree/avl_tree.md
+++ b/docs/chapter_tree/avl_tree.md
@@ -134,14 +134,14 @@ G. M. Adelson-Velsky 和 E. M. Landis 在其 1962 年发表的论文 "An algorit
 
     ```python title="avl_tree.py"
     """ 获取结点高度 """
-    def height(self, node: typing.Optional[TreeNode]) -> int:
+    def height(self, node: Optional[TreeNode]) -> int:
         # 空结点高度为 -1 ，叶结点高度为 0
         if node is not None:
             return node.height
         return -1
     
     """ 更新结点高度 """
-    def __update_height(self, node: TreeNode):
+    def __update_height(self, node: Optional[TreeNode]):
         # 结点高度等于最高子树高度 + 1
         node.height = max([self.height(node.left), self.height(node.right)]) + 1
     ```
@@ -239,7 +239,7 @@ G. M. Adelson-Velsky 和 E. M. Landis 在其 1962 年发表的论文 "An algorit
 
     ```python title="avl_tree.py"
     """ 获取平衡因子 """
-    def balance_factor(self, node: TreeNode) -> int:
+    def balance_factor(self, node: Optional[TreeNode]) -> int:
         # 空结点平衡因子为 0
         if node is None:
             return 0
@@ -355,7 +355,7 @@ AVL 树的独特之处在于「旋转 Rotation」的操作，其可 **在不影
 
     ```python title="avl_tree.py"
     """ 右旋操作 """
-    def __right_rotate(self, node: TreeNode) -> TreeNode:
+    def __right_rotate(self, node: Optional[TreeNode]) -> TreeNode:
         child = node.left
         grand_child = child.right
         # 以 child 为原点，将 node 向右旋转
@@ -470,7 +470,7 @@ AVL 树的独特之处在于「旋转 Rotation」的操作，其可 **在不影
 
     ```python title="avl_tree.py"
     """ 左旋操作 """
-    def __left_rotate(self, node: TreeNode) -> TreeNode:
+    def __left_rotate(self, node: Optional[TreeNode]) -> TreeNode:
         child = node.right
         grand_child = child.left
         # 以 child 为原点，将 node 向左旋转
@@ -621,7 +621,7 @@ AVL 树的独特之处在于「旋转 Rotation」的操作，其可 **在不影
 
     ```python title="avl_tree.py"
     """ 执行旋转操作，使该子树重新恢复平衡 """
-    def __rotate(self, node: TreeNode) -> TreeNode:
+    def __rotate(self, node: Optional[TreeNode]) -> TreeNode:
         # 获取结点 node 的平衡因子
         balance_factor = self.balance_factor(node)
         # 左偏树
@@ -796,7 +796,7 @@ AVL 树的独特之处在于「旋转 Rotation」的操作，其可 **在不影
         return self.root
     
     """ 递归插入结点（辅助函数）"""
-    def __insert_helper(self, node: typing.Optional[TreeNode], val: int) -> TreeNode:
+    def __insert_helper(self, node: Optional[TreeNode], val: int) -> TreeNode:
         if node is None:
             return TreeNode(val)
         # 1. 查找插入位置，并插入结点
@@ -957,7 +957,7 @@ AVL 树的独特之处在于「旋转 Rotation」的操作，其可 **在不影
         return root
     
     """ 递归删除结点（辅助函数） """
-    def __remove_helper(self, node: typing.Optional[TreeNode], val: int) -> typing.Optional[TreeNode]:
+    def __remove_helper(self, node: Optional[TreeNode], val: int) -> Optional[TreeNode]:
         if node is None:
             return None
         # 1. 查找结点，并删除之
diff --git a/docs/chapter_tree/binary_search_tree.md b/docs/chapter_tree/binary_search_tree.md
index e3ddfaaac..a4c5a5d2a 100644
--- a/docs/chapter_tree/binary_search_tree.md
+++ b/docs/chapter_tree/binary_search_tree.md
@@ -83,7 +83,7 @@ comments: true
 
     ```python title="binary_search_tree.py"
     """ 查找结点 """
-    def search(self, num: int) -> typing.Optional[TreeNode]:
+    def search(self, num: int) -> Optional[TreeNode]:
         cur = self.root
         # 循环查找，越过叶结点后跳出
         while cur is not None:
@@ -265,7 +265,7 @@ comments: true
 
     ```python title="binary_search_tree.py"
     """ 插入结点 """
-    def insert(self, num: int) -> typing.Optional[TreeNode]:
+    def insert(self, num: int) -> Optional[TreeNode]:
         root = self.root
         # 若树为空，直接提前返回
         if root is None:
@@ -560,7 +560,7 @@ comments: true
 
     ```python title="binary_search_tree.py"
     """ 删除结点 """
-    def remove(self, num: int) -> typing.Optional[TreeNode]:
+    def remove(self, num: int) -> Optional[TreeNode]:
         root = self.root
         # 若树为空，直接提前返回
         if root is None:
diff --git a/docs/chapter_tree/binary_tree_traversal.md b/docs/chapter_tree/binary_tree_traversal.md
index c64077072..650a15297 100644
--- a/docs/chapter_tree/binary_tree_traversal.md
+++ b/docs/chapter_tree/binary_tree_traversal.md
@@ -66,7 +66,7 @@ comments: true
 
     ```python title="binary_tree_bfs.py"
     """ 层序遍历 """
-    def hier_order(root: TreeNode):
+    def hier_order(root: Optional[TreeNode]):
         # 初始化队列，加入根结点
         queue = collections.deque()
         queue.append(root)
@@ -277,7 +277,7 @@ comments: true
 
     ```python title="binary_tree_dfs.py"
     """ 前序遍历 """
-    def pre_order(root: typing.Optional[TreeNode]):
+    def pre_order(root: Optional[TreeNode]):
         if root is None:
             return
         # 访问优先级：根结点 -> 左子树 -> 右子树
@@ -286,7 +286,7 @@ comments: true
         pre_order(root=root.right)
 
     """ 中序遍历 """
-    def in_order(root: typing.Optional[TreeNode]):
+    def in_order(root: Optional[TreeNode]):
         if root is None:
             return
         # 访问优先级：左子树 -> 根结点 -> 右子树
@@ -295,7 +295,7 @@ comments: true
         in_order(root=root.right)
 
     """ 后序遍历 """
-    def post_order(root: typing.Optional[TreeNode]):
+    def post_order(root: Optional[TreeNode]):
         if root is None:
             return
         # 访问优先级：左子树 -> 右子树 -> 根结点