{
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"source": [
"# 函数装饰器\n",
"\n",
"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",
"\n",
"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",
"\n",
"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",
"\n",
"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。"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## 一、基本语法"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"### 基本装饰器"
]
},
{
"cell_type": "code",
"execution_count": 2,
"metadata": {},
"outputs": [
{
"name": "stdout",
"output_type": "stream",
"text": [
"执行前\n",
"Hello!\n",
"执行后\n"
]
}
],
"source": [
"def my_decorator(func):\n",
" def wrapper():\n",
" print(\"执行前\")\n",
" func()\n",
" print(\"执行后\")\n",
" return wrapper\n",
"\n",
"@my_decorator\n",
"def say_hello():\n",
" print(\"Hello!\")\n",
"\n",
"# 调用函数\n",
"say_hello()"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"### 带参数的装饰器"
]
},
{
"cell_type": "code",
"execution_count": 5,
"metadata": {},
"outputs": [
{
"name": "stdout",
"output_type": "stream",
"text": [
"执行前\n",
"执行后\n",
"8\n",
"执行前\n",
"执行后\n",
"ChinaLanzhou\n"
]
}
],
"source": [
"def my_decorator(func):\n",
" def wrapper(*args, **kwargs):\n",
" print(\"执行前\")\n",
" result = func(*args, **kwargs)\n",
" print(\"执行后\")\n",
" return result\n",
" return wrapper\n",
"\n",
"@my_decorator\n",
"def add(a, b):\n",
" return a + b\n",
"\n",
"# 调用函数\n",
"print(add(3, 5))\n",
"print(add('China', 'Lanzhou'))"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"### 装饰器带参数"
]
},
{
"cell_type": "code",
"execution_count": 7,
"metadata": {},
"outputs": [
{
"name": "stdout",
"output_type": "stream",
"text": [
"你好，小明!\n",
"你好，小明!\n",
"你好，小明!\n"
]
}
],
"source": [
"def repeat(times):\n",
" def decorator(func):\n",
" def wrapper(*args, **kwargs):\n",
" for _ in range(times):\n",
" result = func(*args, **kwargs)\n",
" return result\n",
" return wrapper\n",
" return decorator\n",
"\n",
"@repeat(3)\n",
"def greet(name):\n",
" print(f\"你好，{name}!\")\n",
"\n",
"# 调用函数\n",
"greet(\"小明\")"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"### 二、语法设计动机"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"装饰器的基本语法如下\n",
"\n",
"\n",
"@decorator\n",
"def function_to_decorate(*args, **kwargs):\n",
" # 函数体 \n",
" \n",
"\n",
"这等同于：\n",
"\n",
"def function_to_decorate(*args, **kwargs):\n",
" # 函数体 \n",
"function_to_decorate = decorator(function_to_decorate)\n",
" "
]
},
{
"cell_type": "raw",
"metadata": {},
"source": [
"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",
"wrapper 函数将 func 的结果转换为大写。"
]
},
{
"cell_type": "code",
"execution_count": 12,
"metadata": {},
"outputs": [
{
"name": "stdout",
"output_type": "stream",
"text": [
"HELLO, ALICE!\n"
]
}
],
"source": [
"# 高阶函数的写法\n",
"\n",
"def greet(name):\n",
" return f\"Hello, {name}!\"\n",
"\n",
"def uppercase_decorator(func):\n",
" def wrapper(name):\n",
" result = func(name)\n",
" return result.upper()\n",
" return wrapper\n",
"\n",
"greet_uppercase = uppercase_decorator(greet)\n",
"print(greet_uppercase(\"Alice\"))"
]
},
{
"cell_type": "code",
"execution_count": 13,
"metadata": {},
"outputs": [
{
"name": "stdout",
"output_type": "stream",
"text": [
"HELLO, ALICE!\n"
]
}
],
"source": [
"# 装饰器的写法\n",
"\n",
"def uppercase_decorator(func):\n",
" def wrapper(name):\n",
" result = func(name)\n",
" return result.upper()\n",
" return wrapper\n",
"\n",
"@uppercase_decorator\n",
"def greet(name):\n",
" return f\"Hello, {name}!\"\n",
"\n",
"print(greet(\"Alice\"))"
]
},
{
"cell_type": "raw",
"metadata": {},
"source": [
"在这个例子中，@uppercase_decorator 等价于 greet = uppercase_decorator(greet)。\n",
"使用装饰器，结构更清楚，使用更方便。"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## 三、应用"
]
},
{
"cell_type": "code",
"execution_count": 8,
"metadata": {},
"outputs": [
{
"name": "stdout",
"output_type": "stream",
"text": [
"函数执行完毕\n",
"函数 slow_function 执行时间：1.0016472339630127秒\n"
]
}
],
"source": [
"# 一个简单的计时装饰器\n",
"\n",
"import time\n",
"\n",
"def timer(func):\n",
" def wrapper(*args, **kwargs):\n",
" start = time.time()\n",
" result = func(*args, **kwargs)\n",
" end = time.time()\n",
" print(f\"函数 {func.__name__} 执行时间：{end - start}秒\")\n",
" return result\n",
" return wrapper\n",
"\n",
"@timer\n",
"def slow_function():\n",
" time.sleep(1)\n",
" print(\"函数执行完毕\")\n",
"\n",
"# 调用函数\n",
"slow_function()"
]
},
{
"cell_type": "code",
"execution_count": 11,
"metadata": {},
"outputs": [
{
"data": {
"text/plain": [
"' hello china 2025 '"
]
},
"execution_count": 11,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"### 一个标记文本生成工具\n",
"\n",
"def make_bold(fn): \n",
" def inner(s): return \"\" + fn(s) + \"\" \n",
" return inner\n",
"def make_italic(fn): \n",
" def inner(s): return \"\" + fn(s) + \"\" \n",
" return inner\n",
"\n",
"@make_bold\n",
"@make_italic\n",
"def hello(s) : return s\n",
"\n",
"hello( ' hello china 2025 ')"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## 其它\n",
"\n",
"- 当有多个装饰器时,装饰器的执行顺序是**从下到上**\n",
"- Python 内置了很多实用的装饰器，如 @property、@staticmethod、@classmethod 等\n",
"- 装饰器也可以使用类创建"
]
}
],
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