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On 9 September 2017 at 01:00, Guido van Rossum <guido@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.

Ivan