以python2.7為例說明

【示例一】指定呼叫哪個物件的函式

>>> class Foo(object):
        def func(self):
            print "foo's function"

>>> class Bar(Foo):
        def func(self):
            print "bar's function"

>>> obj = Bar()
>>> # this will call Bar's function
>>> 
 
obj.func()
bar's function
>>> obj.__class__ = Foo  # 指定該物件所屬的類
>>> obj.func()
foo's function
>>> 

【示例二】直接呼叫類的例項，而不是呼叫例項的方法

>>> class Hi(object):
        def __init__(self, x, y):
            self.__x = x
            self.__y = y
        def myfunc(self):
            print
 
 "x=", self.__x, "b=", self.__y

>>> h = Hi("good", "job")
>>> h.myfunc()  # 此處呼叫該例項的方法
x= good b= job
>>> h("ok")   # 無法直接呼叫此類的例項
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-22
 
-d4380afdeffd> in <module>()
----> 1 h("ok")

TypeError: 'Hi' object is not callable
>>> # 如何能直接呼叫例項？這裡有個關鍵的方法__call__()能實現此類的例項可直接呼叫
>>> class Hi(object):
        def __init__(self, x, y):
            self.__x = x
            self.__y = y
        def myfunc(self):
            print "x=", self.__x, "b=", self.__y
        def __call__(self, arg):
            print "call:", arg + self.__x + self.__y

>>> h2 = Hi("nice", "guy")
>>> h2.myfunc()
x= nice b= guy
>>> h2("yeah~")    # __call__ 函式能實現此類的例項可直接呼叫
call: yeah~niceguy

好了，就寫到這裡，看官們覺得漲知識了，請在文章左側點個贊 ^_^