装饰器：本质就是函数，为其他函数添加附加功能，一个原则是不修改函数的源代码，另外一个原则是不修改被修饰函数的调用功能

装饰器=高阶函数+函数嵌套+闭包

前戏

import timedef cal(l):    start_time=time.time()    res=0    for i in l:        time.sleep(0.1)        res+=i    stop_time = time.time()    print('函数的运行时间是%s' %(stop_time-start_time))    return resprint(cal(range(100)))def index():    passdef home():    pass

 装饰器

import timedef timmer(func):    def warpper(*args,**kwargs):        start_time=time.time()        func()        stop_time=time.time()        print("the func run time is %s" % (stop_time-start_time))    return warpper@timmerdef test1():    time.sleep(3)    print("in the test1")test1()结果：in the test1the func run time is 3.0026323795318604