[issue46757] dataclasses should define an empty __post_init__

[Raymond Hettinger]

Raymond Hettinger <raymond.hettin...@gmail.com> added the comment:

Note that adding an empty __post_init__ method would be a breaking change.  The 
following prints out 'B' then 'C'.  But if class A adds an empty __post_init__, 
then 'B' never gets printed.  The arrangement relies on class A being a 
passthrough to class B.

    from dataclasses import dataclass

    @dataclass
    class A:
        pass

    @dataclass
    class B:
        def __post_init__(self):
            print('B')

    @dataclass
    class C(A, B):
        def __post_init__(self):
            super().__post_init__()
            print('C')

    c = C()

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<https://bugs.python.org/issue46757>
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