> On Feb 20, 2018, at 5:38 PM, Guido van Rossum <gu...@python.org> wrote:
>
>> On Tue, Feb 20, 2018 at 1:37 PM, Eric V. Smith <e...@trueblade.com> wrote:
>>> On 2/17/2018 2:35 PM, Guido van Rossum wrote:
>>> PS. I have to ponder why frozen dataclasses don't use `__new__`.
>>
>> As I'm sure everyone is now aware after the rest of this discussion: it's
>> because the returned object isn't really immutable.
>>
>> That said, I have threatened to create a decorator similar to
>> typing.NamedTuple that has the @dataclass features (except maybe
>> __post_init__) and returns a class that does inherit from tuple, in which
>> case it really would use `__new__`. I'll save that for 3.8, if it ever
>> happens. There's a lot there to think about, first. For now,
>> typing.NamedTuple is the way to go if you want something based on namedtuple
>> yet using type hints.
>
> But then the class would also inherit a bunch of misfeatures from tuple (like
> being indexable and having a length).
Right. That’s the “lots to think about” part. It might just be unworkable.
> It would be nicer if it used __slots__ instead. (Also, the problem with
> __slots__ is the same as the problem with inheriting from tuple, and it
> should just be solved right, somehow.)
Agreed.
Eric
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