The simplest explaination on the decorator in Python

decorator in python

the decorator is a function f1, with other function f2 as its parameter, and return a function f3 as its output, with the function of decoration of some other function f2:

 def f1(f2n):  
    def f3():  
        return f2n()*f2n()
    return f3  
@f1  
def f2():  
    return 7
   
print(f2()) ## 返回 49