装饰器

定义：本质是函数，（装饰其他函数）就是为其他函数添加附加功能
原则：
1.不能修改被装饰的函数的源代码
2.不能修改被装饰的函数的调用方法

实现装饰器知识储备
1.函数即“变量”
2.高阶函数　

　　a.把一个函数名当做实参传给另外一个函数
　　b.返回值中包含函数名(不修改函数的调用方式)

3.嵌套函数
高阶函数+嵌套函数==>装饰器

例子：

import time
def timer(func):
    def warpper():
        start_time = time.time()
        func()
        stop_time = time.time()
        print("the fun time is %s"%(stop_time - start_time))
    return  warpper
@timer  #相当于 test1 = warpper(test1)
def test1():
    time.sleep(1)
    print("sleep in test1")

test1()

import time
def timer(func):
    def warpper(*args,**kwargs):#*args,**kwargs可以通用于有不同参数传递
        start_time = time.time()
        func(*args,**kwargs)#*args,**kwargs可以通用于有不同参数传递
        stop_time = time.time()
        print("the fun time is %s"%(stop_time - start_time))
    return  warpper
@timer  #相当于 test1 = warpper(test1)
def test1():
    time.sleep(1)
    print("sleep in test1")
@timer
def test2(name):#因为这里有传递的参数，原来的装饰器不适用，必须增加对应的参数，而为了适应不同的参数传递，所以上方使用args,**kwargs
    time.sleep(1)
    print("name:",name)

test1()
test2("GaShuaiGe")

 带return后，会将函数的结果也返回

import  time
def decorator(func):
    def warper(*args,**kwargs):
        start_time = time.time()
        res = func()
        stop_time = time.time()
        print("in the warper func time is %s"%(stop_time-start_time))
        return res #这个是用来返回函数结果，若没有这个home()里面return "from home"没有
    return  warper


def index():
    print("this is index page")
@decorator
def home():
    time.sleep(1)
    print("this is home page")
    return "from home"
@decorator
def bbs():
    time.sleep(1)
    print("this is bbs page")

index()
print("index()",index())
home()
print("home()",home())
bbs()
print("bbs()",bbs())

 高级版：再嵌套一层

import  time
user , passwd = "alex","123"
def decorator(decorator_type):#将local以及ssh传入
    #print(decorator_type)
    def outwarper(func):
        def warper(*args, **kwargs):
            print("*args, **kwargs",*args, **kwargs)
            if decorator_type == "local":
                username = input("username:").strip()
                password = input("password:").strip()
                if username == user and passwd == password:
                    res = func(*args, **kwargs)
                    print("33[31;1mwelcome！33[0m")
                    return res
                else:
                    print("--------------------------")
                    exit("33[33;1m用户名密码错误！33[0m")
            elif decorator_type =="ssh":
                print("----------------")
                exit("33[33;1m没有ssh！33[0m")

        return warper
    return outwarper

def index():
    print("this is index page")
@decorator(decorator_type = "local")#decorator_type = "local"指定不同的方式
def home():
    time.sleep(1)
    print("this is home page")
    return "from home"

@decorator(decorator_type = "ssh")
def bbs():
    time.sleep(1)
    print("this is bbs page")


index()
#print("index()",index())
home()
#print("home()",home())
bbs()
#print("bbs()",bbs())