On Thu, Dec 12, 2019 at 4:37 PM Eric V. Smith <e...@trueblade.com> wrote:
> On 12/12/2019 8:50 AM, Arthur Pastel wrote: > > On 12/12/2019 8:07 AM, Arthur Pastel wrote: >> >> On Thu, Dec 12, 2019 at 2:03 AM Eric V. Smith <e...@trueblade.com> wrote: >>> >>>> On 12/11/2019 6:36 PM, Arthur Pastel wrote: >>>> >> Add an extra hidden attribute to every instance just >>>> >> to track whether you’re inside __post_init__ so __setattr__ can >>>> check it? >>>> I don't want to add attributes that weren't defined in the class >>>> definition. >>>> >>> Would it be okay if we create an instance attribute before calling the >>> __init__ and then we remove it after the __post_init__ ? >>> Then we would simply have to check for the attribute existence when >>> checking if we raise a FrozenInstanceError. >>> >>> That wouldn't work if the class used __slots__. >>> >> >> Then, in this specific case, would it be possible to add the attribute >> to the __slots__ in the generated class ? >> >> No, __slots__ can't be added or modified after the class exists (which is >> why @dataclass doesn't have an option to add __slots__). >> > > Arg, okay i didn't know. > Then would it be possible to return a child class in the _process_class > function ? It would then be possible to modify the slots. > I'm trying to find a way around this but maybe this is not the good > approach. > > Yes, it is possible. In my github repo I have an add_slots decorator that > does just that. But I don't want the stdlib dataclass decorator to start > returning a different class, without some serious discussion and some > upsides. I don't think making __post_init__ prettier for frozen classes > meets that bar. Although if there's overwhelming support for it here, I > could be convinced to change my mind. > Then what about at least allowing assignment for classes not having __slots__ ?
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