Python装饰器详解-技术圈

装饰器本质就是函数，作用是装饰其它函数，给其它函数增加附加功能，提高代码复用，减少代码量。

我们平时给函数增加新的功能时，通过修改此函数或在函数里调用新的函数实现，但是1、如果这个函数已经是上线的功能，这时修改程序原代码有很大风险 2、如果有100个这样的函数，我们就要找到100个地方进行修改。

例如：我们想新增功能，验证函数执行了多长时间，代码如下：

#修改原函数
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

#原函数内调用新功能的函数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

装饰器原则：

1、不能修改被装饰函数的源代码

2、不能修改被装饰函数的调用方式

实现装饰器储备知识：

高阶函数+嵌套函数=装饰器

1、函数即变量

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、高阶函数

a：把一个函数名当做实参传给另外一个函数(在不修改被装饰函数源代码的情况下为其添加功能)

b：返回值中包含函数名

满足a或b就是高阶函数

def bar():    print('in the bar')def test1(func):    print(func)    func()    return test1test1(bar) #bar的内存地址+调用bar函数print(test1)#test1的内存地址print(test1(bar))#bar的内存地址+调用bar函数+test1的内存地址
"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、嵌套函数

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

不带参数的装饰器：

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

带参数的装饰器：
从实:1中看出@timer相当于test2=timer(test2),timer(func)中func传的是test2,故func=test2
timer(test2)=deco,因为test2=timer(test2)，故test2=deco=func
test2(name,age)=deco(name,age)=func(name,age)所以传参到deco和func里

实例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


实例2：
import time
def timmer(flag):    """    :param flag: 接收装饰器的参数    :return:    """    def outer_wrapper(func):        """        :param func: 接收被装饰的函数        :return:        """        # 接收被装饰函数的参数        def wrapper(*args, **kwargs):            """
            :param args: 收集被装饰函数的参数            :param kwargs: 收集被装饰函数的关键字参数            :return:            """            if flag == "true":                start_time = time.time()                # 调用被装饰的函数                result = func(*args, **kwargs)                # 让进程睡一秒                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