python三大器之裝飾器的練習

裝飾器




加載順序從下至上 執行順序從上至下
'''
多層裝飾器
'''
def deco1(func): #func=deco2    def wrapper1(*args, **kwargs):        '''this is wrapper1'''        print('start 1')        result = func(*args, **kwargs)# wrapper2()        print('end   1')        return result    return wrapper1def deco2(func):#func=deco1    def wrapper2(*args, **kwargs):        '''this is wrapper2'''        print('start 2')        result = func(*args, **kwargs)# wrapper3()        print('end   2')        return result    return wrapper2def deco3(func):#func=foo    def wrapper3(*args, **kwargs):        '''this is wrapper3'''        print('start 3')        result = func(*args, **kwargs)#wrapper1()        print('end   3')        return result    return wrapper3@deco1##deco1(deco2(deco3(foo)))@deco2 #deco2(deco3(foo))@deco3 #deco3(foo)def foo(x, y):    '''this is foo'''    return x * yprint(foo(8, 9))#wrapper1(wrapper2( wrapper3(foo)))執行從外往內'''輸出結果:    start 1    start 2    start 3    end   3    end   2    end   1    72''''''裝飾的過程:    wrapper3 = deco3(foo)    wrapper2 = deco2(wrapper3)    wrapper1 = deco1(wrapper2)    foo = wrapper1執行的過程:正好和裝飾的過程相反。        foo(8, 9)--->wrapper1(8, 9)--->deco1(wrapper2)(8, 9)--->                                                                |                                                                v        deco1( deco2( deco3(foo) ) )(8, 9)<---deco1( deco2(wrapper3) )(8, 9)        類比穿衣服,穿(裝飾)的時候從裏往外一層套一層,脫(執行)的時候從外到裏一層一層脫。'''
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