conchylicultor <etiennefg....@gmail.com> added the comment:
Solving this would significantly improve @dataclass inheritance (https://bugs.python.org/issue39300). Any idea when this will land ? Currently, it is not possible to add required argument to a child dataclass (unless hacks like duplicating attributes): ``` import dataclasses @dataclasses.dataclass class A: x: int = 1 @dataclasses.dataclass class B(A): y: int # ERROR: non-default argument follows default argument ``` Keywords-only would solve this issue: ``` @dataclasses.dataclass class B(A): y: int = dataclasses.field(kw_only=True) B(123, y=456) ``` Note: Attrs already support this: https://www.attrs.org/en/stable/examples.html#keyword-only-attributes For the behavior, I think there are two options: ``` class A: a0: int a1: int = field(kw_only=True) a2: int class B(A): b0: int b1: int = field(kw_only=True) b2: int ``` Option 1: All attributes following `kw_only` are `kw_only` (kw_only indicates where to place '*') A(a0, *, a1, a2) B(a0, b0, *, a1, a2, b1, b2) Option 2: `kw_only` are individually moved to the end A(a0, a2, *, a1) B(a0, a2, b0, b2, *, a1, b1) I personally prefer Option 1, as it makes it easier to place the `*` with less boilerplate. ``` class Request: url: str timeout: int = field(default=-1, kw_only=True) verify: bool = False params: Optional[Dict[str, str]] = None cookies: Optional[Dict[str, str]] = None Request(url, *, timeout=-1, verify=False, params=None, cookies=None) ``` Which looks better than: ``` class Request: url: str timeout: int = field(default=-1, kw_only=True) verify: bool = field(default=False, kw_only=True) params: Optional[Dict[str, str]] = field(default=None, kw_only=True) cookies: Optional[Dict[str, str]] = field(default=None, kw_only=True) ``` ---------- nosy: +conchylicultor _______________________________________ Python tracker <rep...@bugs.python.org> <https://bugs.python.org/issue33129> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
