I resisted adding the ability to set __slots__ in the first version of dataclasses, since it requires that instead of modifying an existing class, an entirely new class is returned.

But I think this feature would be useful enough that I'm now willing to add it. I have the code ready, I just need to work on tests and documentation.

Is the plan to allow an argument to auto-generate __slots__, or would this require repeating the names once in __slots__, and once for annotations and the like?

It would figure it out automatically. See https://github.com/ericvsmith/dataclasses/blob/master/dataclass_tools.py for a decorator that already does this.

I'll have a PR ready soon, I hope.

As a moderately-heavy dataclass user I support this. :)

Hi Eric, I tried to help you with this feature and have opened a PR. I thought that you are too busy to implement this feature, so that's why I decided to help you (It almost two months since your last message in this thread).

New changeset c24199184bea0c851c1a7296ae54aaf18ee56752 by Yurii Karabas in branch 'master':
bpo-42269: Add slots parameter to dataclass decorator (GH-24171)
https://github.com/python/cpython/commit/c24199184bea0c851c1a7296ae54aaf18ee56752

Thanks for all of your work, Yurii.