为什么super（A，self）.__ init __（）不调用A的__init __（）？

Question

class A(object):
    def __init__(self):
        print('A.__init__()')

class D(A):
    def __init__(self):
        super(A, self).__init__()
        print('D.__init__()')

D()

The output is:

D.__init__()

This is unexpected to me. According to my understanding, super(A, self).__init__() should have called A 's ctor, thus should have printed "A. init ()".

I have read a few other questions about super() but I don't think they answer my question exactly.

My python is 3.5.3.

Answer 1

The reason your not getting what you expect is because you are calling the __init__() function of A 's parent class - which is object - so A 's __init__() is never called. You need to do super(D, self).__init__() instead to call the constructor of D 's parent class, A :

>>> class A(object):
    def __init__(self):
        print('A.__init__()')


>>> class D(A):
    def __init__(self):
        super(D, self).__init__() # Change A to D
        print('D.__init__()')


>>> D()
A.__init__()
D.__init__()
<__main__.D object at 0x7fecc5bbcf60>
>>> 

Also, note that in Python 3 you no longer have to explicitly inherit from object . All classes inherit from object by default. See Section 3.3 New-style and old-style classes in Python 2's docs for a more detailed overview.