On Dec 11, 2019, at 08:56, Arthur Pastel <arthur.pas...@gmail.com> wrote: > > When creating frozen dataclasses, attribute initialization must be done > using `object.__setattr__()` it would be nice to allow attribute assignment > in the `__init__` and `__post_init__`.
But how would you implement that? Frozen means that attribute assignment isn’t allowed. The __post_init__ method isn’t magic, it’s just a normal method that gets called normally by the generated __init__. What you’re proposing is that we should make it magic. Which would be useful, but you need to come up with magic that works. If dataclass handled freezeable types (the objects are mutable until you call freeze, after which they’re not), this would be easy (frozen now just means freezable, plus freeze is called by the generated __init__ right after the __post_init__). But it doesn’t, because freezing is complicated. So, what else could you do? Make __setattr__ check the stack and see if it’s being called from type(self).__post_init__? Add an extra hidden attribute to every instance just to track whether you’re inside __post_init__ so __setattr__ can check it? _______________________________________________ Python-ideas mailing list -- python-ideas@python.org To unsubscribe send an email to python-ideas-le...@python.org https://mail.python.org/mailman3/lists/python-ideas.python.org/ Message archived at https://mail.python.org/archives/list/python-ideas@python.org/message/GSSPY5J36JJJHIVQLLWUPWDRSLHAQ653/ Code of Conduct: http://python.org/psf/codeofconduct/
