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裝飾器本質(zhì)就是函數(shù)，作用是裝飾其它函數(shù)，給其它函數(shù)增加附加功能，提高代碼復(fù)用，減少代碼量。

我們平時給函數(shù)增加新的功能時，通過修改此函數(shù)或在函數(shù)里調(diào)用新的函數(shù)實現(xiàn)，但是1、如果這個函數(shù)已經(jīng)是上線的功能，這時修改程序原代碼有很大風(fēng)險? 2、如果有100個這樣的函數(shù)，我們就要找到100個地方進行修改。

例如：我們想新增功能，驗證函數(shù)執(zhí)行了多長時間，代碼如下：

#修改原函數(shù)
import timedef sum1():    start = time.clock()    sum = 1+2    print(sum)    end = time.clock()    print("time used:",end - start)sum1()
"C:\Program Files\Python35\python.exe" C:/Users/wangli/PycharmProjects/Test/Test/test.py3time used: 2.9439962316848234e-05
Process finished with exit code 0

#原函數(shù)內(nèi)調(diào)用新功能的函數(shù)import timedef sum1():    sum = 1+ 2    print (sum)def timeit(func):    start = time.clock()    func()    end =time.clock()    print("time used:", end - start)timeit(sum1)
"C:\Program Files\Python35\python.exe" C:/Users/wangli/PycharmProjects/Test/Test/test.py3time used: 3.071996067845033e-05
Process finished with exit code 0

裝飾器原則：

1、不能修改被裝飾函數(shù)的源代碼

2、不能修改被裝飾函數(shù)的調(diào)用方式

實現(xiàn)裝飾器儲備知識：

高階函數(shù)+嵌套函數(shù)=裝飾器

1、函數(shù)即變量

def test1():    print('hello！')    return test1test2=test1test2()print(test2)
"C:\Program Files\Python35\python.exe" C:/Users/wangli/PycharmProjects/Test/Test/test.pyhello！0x0000018E5D1A8F28>
Process finished with exit code 0

2、高階函數(shù)

a：把一個函數(shù)名當(dāng)做實參傳給另外一個函數(shù)(在不修改被裝飾函數(shù)源代碼的情況下為其添加功能)

b：返回值中包含函數(shù)名

滿足a或b就是高階函數(shù)

def bar():    print('in the bar')def test1(func):    print(func)    func()    return test1test1(bar) #bar的內(nèi)存地址+調(diào)用bar函數(shù)print(test1)#test1的內(nèi)存地址print(test1(bar))#bar的內(nèi)存地址+調(diào)用bar函數(shù)+test1的內(nèi)存地址
"C:\Program Files\Python35\python.exe" C:/Users/wangli/PycharmProjects/Test/Test/test.py0x0000026AC7C58F28>in the bar
0x0000026AC82C89D8>

0x0000026AC7C58F28>in the bar0x0000026AC82C89D8>
Process finished with exit code 0



import timedef bar():    time.sleep(3)    print('in the bar')def test1(func):    start_time=time.time()    func()    stop_time=time.time()    print('the func run time is %s'%(stop_time-start_time))    return funcbar=test1(bar)bar()

"C:\Program Files\Python35\python.exe" C:/Users/wangli/PycharmProjects/Test/Test/test.pyin the barthe func run time is 3.0008511543273926in the bar
Process?finished?with?exit?code?0

3、嵌套函數(shù)

def foo():    print('in the foo')    def bar():        print('in the bar')    bar()foo()
"C:\Program Files\Python35\python.exe" C:/Users/wangli/PycharmProjects/Test/Test/test.pyin the fooin the bar
Process finished with exit code 0

不帶參數(shù)的裝飾器：

import timedef timer(func):    def deco():        start_time=time.time()        func()        stop_time=time.time()        print('the func run time is %s'%(stop_time-start_time))    return deco@timer    #test1=timer(test1)def test1():    time.sleep(3)    print('in the test1')test1()

"C:\Program Files\Python35\python.exe" C:/Users/wangli/PycharmProjects/Test/Test/test.pyin the test1the func run time is 3.000833511352539
Process finished with exit code 0

帶參數(shù)的裝飾器：
從實:1中看出@timer相當(dāng)于test2=timer(test2),timer(func)中func傳的是test2,故func=test2
timer(test2)=deco,因為test2=timer(test2)，故test2=deco=func
test2(name,age)=deco(name,age)=func(name,age)所以傳參到deco和func里

實例1：import timedef timer(func):    def deco(*args,**kwargs):        start_time=time.time()        func(*args,**kwargs)        stop_time=time.time()        print('the func run time is %s'%(stop_time-start_time))    return deco@timer #test1=timer(test1)def test1():    time.sleep(3)    print('in the test1')test1()@timer  #test2=timer(test2)def test2(name,age):    time.sleep(3)    print('%s %s in the test2'%(name,age))test2('wangli',22)
"C:\Program Files\Python35\python.exe" C:/Users/wangli/PycharmProjects/Test/Test/test.pyin the test1the func run time is 3.0001492500305176wangli 22 in the test2the func run time is 3.000540256500244
Process finished with exit code 0


實例2：
import time
def timmer(flag):    """    :param flag: 接收裝飾器的參數(shù)    :return:    """    def outer_wrapper(func):        """        :param func: 接收被裝飾的函數(shù)        :return:        """        # 接收被裝飾函數(shù)的參數(shù)        def wrapper(*args, **kwargs):            """
            :param args: 收集被裝飾函數(shù)的參數(shù)            :param kwargs: 收集被裝飾函數(shù)的關(guān)鍵字參數(shù)            :return:            """            if flag == "true":                start_time = time.time()                # 調(diào)用被裝飾的函數(shù)                result = func(*args, **kwargs)                # 讓進程睡一秒                time.sleep(1)                stop_time = time.time()                print("{func} spend {time} ".format(func="add", time=stop_time - start_time))                return result            else:                print("Unexpected ending")        return wrapper    return outer_wrapper

Python裝飾器詳解