On 3/16/2021 9:48 AM, Ricky Teachey wrote:
On Tue, Mar 16, 2021 at 9:23 AM Eric V. Smith <firstname.lastname@example.org mailto:email@example.com> wrote:
On 3/16/2021 7:01 AM, Simão Afonso @ Powertools Tech wrote: >> The problem is that if you have 1 normal parameter and 10 keyword-only >> ones, you'd be forced to say: >> >> @dataclasses.dataclass >> class LotsOfFields: >> a: Any >> b: Any = field(kw_only=True, default=0) >> c: Any = field(kw_only=True, default='foo') >> d: Any = field(kw_only=True) >> e: Any = field(kw_only=True, default=0.0) >> f: Any = field(kw_only=True) >> g: Any = field(kw_only=True, default=()) >> h: Any = field(kw_only=True, default='bar') >> i: Any = field(kw_only=True, default=3+4j) >> j: Any = field(kw_only=True, default=10) >> k: Any = field(kw_only=True) >> >> That's way too verbose for me.
Here's another option I just thought of, that might have some strengths:
@dataclasses.dataclass class LotsOfFields: # first member assumed to be kw_or_posit unless marked otherwise a: Any # start kw only here because `mark= dataclasses.KW_ONLY` b: Any = field(default=0, mark=dataclasses.KW_ONLY) # all members following above line continue to be kw_only c: Any = 'foo' d: Any e: Any = 0.0 f: Any g: Any = () h: Any = 'bar' i: Any = 3+4j j: Any = 10 k: Any
I changed the kw argument name from `kw_only` to `mark`.
The idea is that every supplied member (above, members c through k) is assumed to have the same `mark` as the most recently explicitly designated field (above, member b). Or, if there has not yet been an explicitly designated `mark` for a member, the first field (above, member a) is assumed to be `dataclasses.KW_OR_POSIT` (or whatever other singleton name makes sense).
In this way we only have to use the field() call once, we can go back and forth, we eliminate a line like `_: dataclasses.KW_OPTIONAL` that to some people might be a bit inscrutable, and we leave the door open to support positional arguments in the future (perhaps through something like `mark= dataclasses.KW_OR_POSIT`) if it becomes desirable for some reason.
I prefer the "_: dataclasses.KW_ONLY" version, because it more closely matches "def foo(a, *, b, c, d)". The "everything else is a keyword" isn't attached to one parameter, it's between parameters.
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