Python's Decorator

A: Decorative essence is a function, function is to add additional functions for other functions

II: Principle:

1) Do not modify the source code of the modified function

2) Do not modify the calling method of the modified function

Three: the implementation of the adorner

1) Adorner = higher order function + function nesting + closure

Example: Add the following function to the function of an execution time

Import Timedef cal (L):    res=0 for    i in L:        res+=i    return resret=cal (range) print (ret)

In order to ensure the principle of the adorner, we need to write another function of execution time

Add adorners to functions to print out run-time function def timer (func):    def wapper (*args,*kwargs):        starttime = time.time ()        res = func (* Args,**kwargs)        stoptime = Time.time ()        print ("Function run time:%s"% (stoptime-starttime))        return  Res    Return Wapper

Adorner usage: Declare it in the first function to @timer

@timerdef cal (L):    res=0 for    i in L:        res+=i    return resret=cal (range) print (ret)

　　

　

Python's Decorator