On Tue, Mar 16, 2021 at 9:23 AM Eric V. Smith eric@trueblade.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.
--- Ricky.
"I've never met a Kentucky man who wasn't either thinking about going home or actually going home." - Happy Chandler