Python 装饰器入门

装饰器是 Python 的强大特性，可以在不修改原函数的情况下增强其功能。

1. 基本装饰器

def my_decorator(func):
    def wrapper():
        print("调用前")
        func()
        print("调用后")
    return wrapper

@my_decorator
def say_hello():
    print("Hello!")

say_hello()
# 输出:
# 调用前
# Hello!
# 调用后

2. 带参数的装饰器

def repeat(times):
    def decorator(func):
        def wrapper(*args, **kwargs):
            for _ in range(times):
                result = func(*args, **kwargs)
            return result
        return wrapper
    return decorator

@repeat(times=3)
def say_hi():
    print("Hi!")

say_hi()

3. 保留原函数信息

from functools import wraps

def my_decorator(func):
    @wraps(func)
    def wrapper(*args, **kwargs):
        print("调用前")
        return func(*args, **kwargs)
    return wrapper

@my_decorator
def greet(name):
    """问候函数"""
    return f"Hello, {name}"

print(greet.__name__)  # greet
print(greet.__doc__)   # 问候函数

4. 常用内置装饰器

class MyClass:
    @staticmethod
    def static_method():
        pass
    
    @classmethod
    def class_method(cls):
        pass
    
    @property
    def prop(self):
        return self._value

5. 装饰器实际应用

计时装饰器

import time
from functools import wraps

def timer(func):
    @wraps(func)
    def wrapper(*args, **kwargs):
        start = time.time()
        result = func(*args, **kwargs)
        print(f"耗时: {time.time() - start:.2f}秒")
        return result
    return wrapper

@timer
def slow_function():
    time.sleep(1)

日志装饰器

def log(func):
    @wraps(func)
    def wrapper(*args, **kwargs):
        print(f"调用 {func.__name__}")
        result = func(*args, **kwargs)
        print(f"{func.__name__} 返回: {result}")
        return result
    return wrapper

缓存装饰器

from functools import lru_cache

@lru_cache(maxsize=128)
def fibonacci(n):
    if n < 2:
        return n
    return fibonacci(n-1) + fibonacci(n-2)

装饰器是 Python 开发中的重要技能，掌握它能写出更优雅的代码。