Python装饰器（Decorators）深度解析

Python装饰器（Decorators）深度解析

作为一名从后端开发转向Rust的开发者，我发现Python的装饰器与Rust的特质（Traits）有一些相似之处，它们都可以用于扩展代码的功能。今天我想分享一下我对Python装饰器的理解和实践。

什么是装饰器？

装饰器是一种特殊的函数，它可以修改其他函数或类的行为。装饰器的语法使用@符号，放在被装饰函数或类的定义之前。

@decorator def function(): pass

这相当于：

def function(): pass function = decorator(function)

装饰器的基本实现

1. 简单装饰器

def simple_decorator(func): def wrapper(): print("Before function execution") func() print("After function execution") return wrapper @simple_decorator def hello(): print("Hello, world!") # 调用函数 hello()

输出：

Before function execution Hello, world! After function execution

2. 带参数的装饰器

def decorator_with_args(prefix): def decorator(func): def wrapper(): print(f"{prefix}: Before function execution") func() print(f"{prefix}: After function execution") return wrapper return decorator @decorator_with_args("LOG") def hello(): print("Hello, world!") # 调用函数 hello()

输出：

LOG: Before function execution Hello, world! LOG: After function execution

3. 保留函数元数据的装饰器

import functools def decorator_with_metadata(func): @functools.wraps(func) def wrapper(): print("Before function execution") func() print("After function execution") return wrapper @decorator_with_metadata def hello(): """Print hello message""" print("Hello, world!") # 调用函数 hello() # 查看函数元数据 print(f"Function name: {hello.__name__}") print(f"Function docstring: {hello.__doc__}")

输出：

Before function execution Hello, world! After function execution Function name: hello Function docstring: Print hello message

4. 带参数的函数装饰器

import functools def decorator_with_args_and_function_args(func): @functools.wraps(func) def wrapper(*args, **kwargs): print("Before function execution") result = func(*args, **kwargs) print("After function execution") return result return wrapper @decorator_with_args_and_function_args def add(a, b): """Add two numbers""" return a + b # 调用函数 result = add(1, 2) print(f"Result: {result}") # 查看函数元数据 print(f"Function name: {add.__name__}") print(f"Function docstring: {add.__doc__}")

输出：

Before function execution After function execution Result: 3 Function name: add Function docstring: Add two numbers

装饰器的高级用法

1. 类装饰器

class ClassDecorator: def __init__(self, func): self.func = func def __call__(self, *args, **kwargs): print("Before function execution") result = self.func(*args, **kwargs) print("After function execution") return result @ClassDecorator def hello(): print("Hello, world!") # 调用函数 hello()

输出：

Before function execution Hello, world! After function execution

2. 带参数的类装饰器

class ClassDecoratorWithArgs: def __init__(self, prefix): self.prefix = prefix def __call__(self, func): def wrapper(*args, **kwargs): print(f"{self.prefix}: Before function execution") result = func(*args, **kwargs) print(f"{self.prefix}: After function execution") return result return wrapper @ClassDecoratorWithArgs("LOG") def hello(): print("Hello, world!") # 调用函数 hello()

输出：

LOG: Before function execution Hello, world! LOG: After function execution

3. 装饰器链

import functools def decorator1(func): @functools.wraps(func) def wrapper(*args, **kwargs): print("Decorator 1: Before function execution") result = func(*args, **kwargs) print("Decorator 1: After function execution") return result return wrapper def decorator2(func): @functools.wraps(func) def wrapper(*args, **kwargs): print("Decorator 2: Before function execution") result = func(*args, **kwargs) print("Decorator 2: After function execution") return result return wrapper @decorator1 @decorator2 def hello(): print("Hello, world!") # 调用函数 hello()

输出：

Decorator 1: Before function execution Decorator 2: Before function execution Hello, world! Decorator 2: After function execution Decorator 1: After function execution

4. 装饰器用于类方法

import functools def method_decorator(func): @functools.wraps(func) def wrapper(self, *args, **kwargs): print("Before method execution") result = func(self, *args, **kwargs) print("After method execution") return result return wrapper class MyClass: @method_decorator def hello(self): print("Hello, world!") # 创建实例并调用方法 obj = MyClass() obj.hello()

输出：

Before method execution Hello, world! After method execution

装饰器的应用场景

1. 日志记录

import functools import time def log_execution(func): @functools.wraps(func) def wrapper(*args, **kwargs): start_time = time.time() print(f"Executing {func.__name__}...") result = func(*args, **kwargs) end_time = time.time() print(f"{func.__name__} executed in {end_time - start_time:.4f} seconds") return result return wrapper