CODEWITHSUNDEEP
pythonpython-3.xsuper
Roy
Roy

Reputation: 945

Why super(A, self).__init__() doesn't call A's __init__()?

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.

Upvotes: 1

Views: 629

Answers (1)

Chris
Chris

Reputation: 22953

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.

Upvotes: 2

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