python 装饰器例子

from functools import wraps


def logit(func):
    @wraps(func)
    def with_logging(*args, **kwargs):
        print(func.__name__ + " was called")
        return func(*args, **kwargs)

    return with_logging

@logit
def addition_func(x):
    return x + x


result = addition_func(4)

1. 遇到@logit , 开始执行 logit 函数，并把 “addition_func”作为参数去代替 “func”

2. 把 “additon_func" 替换为 with_logging 函数

3 . 把 "with_logging "函数读入内存中。

4 . 执行 result = addition_func(4)

 　　　这时候执行 with_logging (4)

　　　　print(func.__name__ + " was called") ===> " addition_func was called"

　　　　retrun func(*args,**kwargs) ====> additon_func(4)=8 ===>result