装饰器

1 开放封闭原则

1. 拓展是开放的 (增加新功能)
2. 修改源码是封闭的 (修改已经实现的功能)

在不改变源代码及调用方式的基础上额外增加新的功能

2 装饰器 (用来装饰的工具)

2.1标准版装饰器:

def wrapper(func):
    def inner(*args,**kwargs):
        '''执行被装饰函数之前的操作'''
        ret = func(*args,**kwargs)
        '''执行被装饰函数之后的操作'''
        return ret
    return inner

语法糖: 必须放在被装饰的函数正上方

import time
def times(f):
    def inner():
        start_time = time.time()
        ret = f()
        end_time = time.time()
        print(end_time - start_time)
        return ret
    return inner
@times  #相当于foo = times(foo)
def foo():
    time.sleep(3) #模拟网络延迟
    print('111')
# foo = times(foo)
foo()

2.2带参数的装饰器

def auth(argv):
    def wrapper(f):
        def inner():
            ret = f()
            if argv == 'QQ':
                print('QQ登陆成功!')
            elif argv == '微信':
                print('微信登录成功!')
            else:
                print('邮箱登陆成功!')
        return inner
    return wrapper
choose = input('>>>')
@auth(choose)
def func():
    pass
func()

2.3多个装饰器装饰一个函数

def wrapper1(f):  # f = inner2
    def inner1(*args,**kwargs):
        print(1)
        ret = f(*args,**kwargs)
        print(11)
        return ret
    return inner1

def wrapper2(f):  # f = inner3
    def inner2(*args,**kwargs):
        print(2)
        ret = f(*args,**kwargs)
        print(22)
        return ret
    return inner2

def wrapper3(f):  # f = func
    def inner3(*args,**kwargs):
        print(3)
        ret = f(*args,**kwargs)
        print(33)
        return ret
    return inner3

@wrapper1
@wrapper2
@wrapper3
def func():
    print(4)
func()

func = wrapper3(func) # func = inner3
func = wrapper2(func) # inner2 = wrapper2(inner3)
func = wrapper1(func)  # inner1 = wrapper1(inner2)
func()                 #inner1()