On 3/16/2021 9:48 AM, Ricky Teachey wrote:
On Tue, Mar 16, 2021 at 9:23 AM Eric V. Smith <e...@trueblade.com
<mailto:e...@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.
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.
Eric
---
Ricky.
"I've never met a Kentucky man who wasn't either thinking about going
home or actually going home." - Happy Chandler
--
Eric V. Smith
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