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super() weirdness in Python 3
原标题:

I know this has been discussed a number of times before, but there was never an explanation of what s going on "under the hood".

Can anyone provide a detailed explanation as to why commenting-in the last line of code causes an error to be raised? I know that that object.__init__ doesn t take any arguments, but why does the code work when the line is commented out?

class A:
   def __init__(self, a):
      print("A constructor")
      super().__init__(a)
      self.a = a
      print("A constructor end")

class B:
   def __init__(self, b):
      print("B constructor")
      super().__init__()
      self.b = b
      print("B constructor end")


class C(A, B):
   def __init__(self, x):
      super().__init__(x)


c = C(42)
#a = A(33)
最佳回答

In Python 3 every method becomes a closure with a hidden value added for the "current class" being defined. This is accessed by super() (with no arguments).

Super returns an object which uses the class s Method Resolution Order (MRO), and for C instances this has B after A.

Without finding B in the MRO, super().__init__ in A will call object.__init__, to which you can t pass any parameters.

You can view the MRO for a class by looking at SomeClass.__mro__.

Though mostly talking about 2.x, you may want to read http://fuhm.net/super-harmful/.

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