[Python-Dev] PEP 557: Data Classes (original) (raw)

Ivan Levkivskyi levkivskyi at gmail.com
Fri Sep 8 19:19:20 EDT 2017

On 9 September 2017 at 01:00, Guido van Rossum <guido at python.org> wrote:

I think it would be useful to write 1-2 sentences about the problem with inheritance -- in that case you pretty much have to use a metaclass,

It is not the case now. I think init_subclass has almost the same possibilities as a decorator, it just updates an already created class and can add some methods to it. This is a more subtle question, these two for example would be equivalent:

from dataclass import Data, Frozen

class Point(Frozen, Data): x: int y: int

and

from dataclass import dataclass

@dataclass(frozen=True) class Point: x: int y: int

But the problem with inheritance based pattern is that it cannot support automatic addition of slots. Also I think a decorator will be easier to maintain. But on the other hand I think inheritance based scheme is a bit more readable.

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