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{
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"cells": [
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"# 函数装饰器\n",
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"\n",
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"装饰器（Decorator）是 Python 中一个非常重要的概念，装饰器在不修改原函数代码的情况下，给原函数动态地增加功能。\n",
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"\n",
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"装饰器本质上是一个高阶函数，它接受一个函数作为参数并返回一个新的函数。\n",
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"\n",
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"装饰器的常见用途：日志记录、性能测试、权限验证、缓存、事务处理等\n",
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"\n",
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"装饰器是 Python 中非常强大的特性，合理使用可以让代码更加简洁、优雅，并且符合 DRY（Don't Repeat Yourself）原则。"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## 一、基本语法"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"### 基本装饰器"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 2,
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"metadata": {},
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"outputs": [
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{
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"name": "stdout",
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"output_type": "stream",
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"text": [
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"执行前\n",
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"Hello!\n",
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"执行后\n"
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]
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}
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],
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"source": [
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"def my_decorator(func):\n",
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" def wrapper():\n",
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" print(\"执行前\")\n",
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" func()\n",
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" print(\"执行后\")\n",
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" return wrapper\n",
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"\n",
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"@my_decorator\n",
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"def say_hello():\n",
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" print(\"Hello!\")\n",
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"\n",
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"# 调用函数\n",
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"say_hello()"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"### 带参数的装饰器"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 5,
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"metadata": {},
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"outputs": [
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{
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"name": "stdout",
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"output_type": "stream",
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"text": [
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"执行前\n",
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"执行后\n",
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"8\n",
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"执行前\n",
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"执行后\n",
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"ChinaLanzhou\n"
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]
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}
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],
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"source": [
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"def my_decorator(func):\n",
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" def wrapper(*args, **kwargs):\n",
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" print(\"执行前\")\n",
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" result = func(*args, **kwargs)\n",
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" print(\"执行后\")\n",
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" return result\n",
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" return wrapper\n",
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"\n",
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"@my_decorator\n",
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"def add(a, b):\n",
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" return a + b\n",
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"\n",
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"# 调用函数\n",
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"print(add(3, 5))\n",
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"print(add('China', 'Lanzhou'))"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"### 装饰器带参数"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 7,
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"metadata": {},
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"outputs": [
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{
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"name": "stdout",
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"output_type": "stream",
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"text": [
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"你好，小明!\n",
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"你好，小明!\n",
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"你好，小明!\n"
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]
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}
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],
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"source": [
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"def repeat(times):\n",
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" def decorator(func):\n",
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" def wrapper(*args, **kwargs):\n",
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" for _ in range(times):\n",
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" result = func(*args, **kwargs)\n",
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" return result\n",
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" return wrapper\n",
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" return decorator\n",
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"\n",
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"@repeat(3)\n",
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"def greet(name):\n",
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" print(f\"你好，{name}!\")\n",
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"\n",
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"# 调用函数\n",
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"greet(\"小明\")"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"### 二、语法设计动机"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"装饰器的基本语法如下\n",
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"\n",
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"<code>\n",
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"@decorator\n",
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"def function_to_decorate(*args, **kwargs):\n",
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" # 函数体 \n",
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"</code> \n",
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"\n",
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"这等同于：\n",
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"<code>\n",
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"def function_to_decorate(*args, **kwargs):\n",
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" # 函数体 \n",
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"function_to_decorate = decorator(function_to_decorate)\n",
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"</code> "
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]
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},
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{
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"cell_type": "raw",
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"metadata": {},
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"source": [
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"在下面例子中，uppercase_decorator 接受一个函数 func 作为参数，并返回一个新的函数 wrapper。\n",
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"wrapper 函数将 func 的结果转换为大写。"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 12,
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"metadata": {},
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"outputs": [
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{
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"name": "stdout",
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"output_type": "stream",
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"text": [
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"HELLO, ALICE!\n"
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]
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}
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],
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"source": [
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"# 高阶函数的写法\n",
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"\n",
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"def greet(name):\n",
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" return f\"Hello, {name}!\"\n",
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"\n",
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"def uppercase_decorator(func):\n",
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" def wrapper(name):\n",
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" result = func(name)\n",
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" return result.upper()\n",
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" return wrapper\n",
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"\n",
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"greet_uppercase = uppercase_decorator(greet)\n",
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"print(greet_uppercase(\"Alice\"))"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 13,
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"metadata": {},
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"outputs": [
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{
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"name": "stdout",
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"output_type": "stream",
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"text": [
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"HELLO, ALICE!\n"
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]
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}
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],
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"source": [
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"# 装饰器的写法\n",
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"\n",
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"def uppercase_decorator(func):\n",
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" def wrapper(name):\n",
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" result = func(name)\n",
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" return result.upper()\n",
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" return wrapper\n",
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"\n",
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"@uppercase_decorator\n",
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"def greet(name):\n",
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" return f\"Hello, {name}!\"\n",
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"\n",
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"print(greet(\"Alice\"))"
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]
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},
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{
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"cell_type": "raw",
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"metadata": {},
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"source": [
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"在这个例子中，@uppercase_decorator 等价于 greet = uppercase_decorator(greet)。\n",
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"使用装饰器，结构更清楚，使用更方便。"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## 三、应用"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 8,
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"metadata": {},
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"outputs": [
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{
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"name": "stdout",
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"output_type": "stream",
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"text": [
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"函数执行完毕\n",
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"函数 slow_function 执行时间：1.0016472339630127秒\n"
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]
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}
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],
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"source": [
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"# 一个简单的计时装饰器\n",
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"\n",
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"import time\n",
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"\n",
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"def timer(func):\n",
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" def wrapper(*args, **kwargs):\n",
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" start = time.time()\n",
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" result = func(*args, **kwargs)\n",
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" end = time.time()\n",
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" print(f\"函数 {func.__name__} 执行时间：{end - start}秒\")\n",
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" return result\n",
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" return wrapper\n",
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"\n",
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"@timer\n",
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"def slow_function():\n",
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" time.sleep(1)\n",
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" print(\"函数执行完毕\")\n",
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"\n",
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"# 调用函数\n",
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"slow_function()"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 11,
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"metadata": {},
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"outputs": [
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{
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"data": {
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"text/plain": [
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"'<b><i> hello china 2025 </i></b>'"
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]
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},
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"execution_count": 11,
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"metadata": {},
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"output_type": "execute_result"
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}
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],
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"source": [
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"### 一个标记文本生成工具\n",
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"\n",
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"def make_bold(fn): \n",
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" def inner(s): return \"<b>\" + fn(s) + \"</b>\" \n",
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" return inner\n",
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"def make_italic(fn): \n",
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" def inner(s): return \"<i>\" + fn(s) + \"</i>\" \n",
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" return inner\n",
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"\n",
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"@make_bold\n",
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"@make_italic\n",
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"def hello(s) : return s\n",
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"\n",
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"hello( ' hello china 2025 ')"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## 其它\n",
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"\n",
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"- 当有多个装饰器时,装饰器的执行顺序是**从下到上**\n",
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"- Python 内置了很多实用的装饰器，如 @property、@staticmethod、@classmethod 等\n",
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"- 装饰器也可以使用类创建"
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]
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}
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],
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"metadata": {
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"hide_input": false,
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"kernelspec": {
|
|
|
|
|
"display_name": "Python 3",
|
|
|
|
|
"language": "python",
|
|
|
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"name": "python3"
|
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|
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},
|
|
|
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"language_info": {
|
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|
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|
"codemirror_mode": {
|
|
|
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|
"name": "ipython",
|
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"version": 3
|
|
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},
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|
"file_extension": ".py",
|
|
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"mimetype": "text/x-python",
|
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|
"name": "python",
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"nbconvert_exporter": "python",
|
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|
"pygments_lexer": "ipython3",
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|
|
"version": "3.8.3"
|
|
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|
|
}
|
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},
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"nbformat": 4,
|
|
|
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"nbformat_minor": 4
|
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}
|
