Python 装饰器

Python 装饰器

1. 简单的装饰器

下面是一个简单的装饰器示例，它记录被装饰函数的调用信息：

def my_decorator(func):
    """ 中层函数：接收被装饰的函数 """
    def wrapper():
         """ 内层函数：执行具体功能 """
        print("Something is happening before the function is called.")
        func()
        print("Something is happening after the function is called.")
    return wrapper

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

say_hello()
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def my_decorator(func):
    def wrapper(x):
        print("Something is happening before the function is called.")
        func(x)
        print("Something is happening after the function is called.")
    return wrapper

@my_decorator
def say_hello(x):
    print(f"Hello!   {x}")

say_hello('xiao ming ')

# 这样更统一
def my_decorator(func):
    def wrapper(*args, **kwargs):
        print("Something is happening before the function is called.")
        func(*args, **kwargs)
        print("Something is happening after the function is called.")
    return wrapper

@my_decorator
def say_hello(x):
    print(f"Hello!   {x}")

say_hello('xiao ming ')
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带参数直接在内层函数添加

2. 装饰器带参数

def repeat(num_times):
    def my_decorator(func):
        def wrapper(x):
            for i in range(num_times):
                print(f"Something is happening before the function is called.{i}")
                func(x)
                print(f"Something is happening after the function is called.{i}", end='\n\n')
        return wrapper
    return my_decorator
@repeat(3)
def say_hello(x):
    print(f"Hello!   {x}")

say_hello('xiao ming ')

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问题：定义一个装饰器，可以计算函数的执行时间

import time
def times(num_times):
    def decorated(func):
        def wrapper(x):
            times = 0
            for _ in range(num_times):
                start = time.time()
                ret = func(x)
                times += time.time() - start
            print(f"Average execution time over {num_times} runs: {times:.6f} seconds")
            times /= num_times
            return ret
        return wrapper
    return decorated

@times(5)
def func(n):
    cnt = 0
    for i in range(1, n+1):
        cnt += i
    return cnt
func(1000000)
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3. 类调用

class CountCalls:
    def __init__(self, func):
        self.func = func
        self.num_calls = 0

    def __call__(self, *args, **kwargs):
        self.num_calls += 1
        print(f"Call {self.num_calls} of {self.func.__name__}")
        return self.func(*args, **kwargs)

@CountCalls
def say_hello():
    print("Hello!")
say_hello()
say_hello()
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  return self.func(*args, **kwargs)
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@CountCalls
def say_hello():
print(“Hello!”)
say_hello()
say_hello()

![image-20240425211803257](https://img-blog.csdnimg.cn/img_convert/481ee58543025ee56ecb85999ee96094.png)
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