correct way to use super (argument passing)

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迷失自我
迷失自我 2020-11-29 16:29

So I was following Python\'s Super Considered Harmful, and went to test out his examples.

However, Example 1-3, which is supposed to show the correct way of calling

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  •  眼角桃花
    2020-11-29 17:06

    Sometimes two classes may have some parameter names in common. In that case, you can't pop the key-value pairs off of **kwargs or remove them from *args. Instead, you can define a Base class which unlike object, absorbs/ignores arguments:

    class Base(object):
        def __init__(self, *args, **kwargs): pass
    
    class A(Base):
        def __init__(self, *args, **kwargs):
            print "A"
            super(A, self).__init__(*args, **kwargs)
    
    class B(Base):
        def __init__(self, *args, **kwargs):
            print "B"
            super(B, self).__init__(*args, **kwargs)
    
    class C(A):
        def __init__(self, arg, *args, **kwargs):
            print "C","arg=",arg
            super(C, self).__init__(arg, *args, **kwargs)
    
    class D(B):
        def __init__(self, arg, *args, **kwargs):
            print "D", "arg=",arg
            super(D, self).__init__(arg, *args, **kwargs)
    
    class E(C,D):
        def __init__(self, arg, *args, **kwargs):
            print "E", "arg=",arg
            super(E, self).__init__(arg, *args, **kwargs)
    
    print "MRO:", [x.__name__ for x in E.__mro__]
    E(10)
    

    yields

    MRO: ['E', 'C', 'A', 'D', 'B', 'Base', 'object']
    E arg= 10
    C arg= 10
    A
    D arg= 10
    B
    

    Note that for this to work, Base must be the penultimate class in the MRO.

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