It's been two years since this proposal has been postponed - I would like to revive it.
A quick recap (quotes edited for brevity): > > > On 23 January 2018 at 03:33, George Leslie-Waksman > > > <waks...@gmail.com mailto:waks...@gmail.com> wrote: > > > > > > The proposed implementation of dataclasses prevents defining > > > fields with defaults before fields without defaults. This can > > > create limitations on logical grouping of fields and on > > > inheritance. > > > > > > Take, for example, the case: > > > > > > @dataclass > > > class Foo: > > > some_default: dict = field(default_factory=dict) > > > > > > @dataclass > > > class Bar(Foo): > > > other_field: int > > > > > > this results in the error: > > > TypeError: non-default argument 'other_field' follows default > > > argument > > > > > > I understand that this is a limitation of positional arguments > > > because the effective __init__ signature is: > > > > > > def __init__(self, some_default: dict = <something>, > > > other_field: int): > > > > > > However, keyword only arguments allow an entirely reasonable > > > solution to this problem: > > > > > > def __init__(self, *, some_default: dict = <something>, > > > other_field: int): > > > > > > And have the added benefit of making the fields in the > > __init__ > > > call entirely explicit. > > > > > > So, I propose the addition of a keyword_only flag to the > > > @dataclass decorator that renders the __init__ method using > > > keyword only arguments: > > > > > > @dataclass(keyword_only=True) > > > class Bar(Foo): > > > other_field: int > > > > > > --George Leslie-Waksman Guido van Rossum wrote: > We can reconsider for 3.8. > --Guido van Rossum (python.org/~guido) What do you think about implementing this now? What should be the next step? Would it require a PEP? _______________________________________________ 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/Y3N6DIC4NLXY36GLZCXHE4NPO4VTNBGS/ Code of Conduct: http://python.org/psf/codeofconduct/
