> On 7 Oct 2021, at 18:41, S Pradeep Kumar <[email protected]> wrote: > > Note that we considered and rejected using a full def-signature syntax like > ```` > (record: PurchaseRecord, permissions: List[AuthPermission], /) -> > FormattedItem > ```` > because it would be more verbose for common cases and could lead to subtle > bugs; more details in [3].
Is this also why re-using an actual callable at a type was rejected? I always found the following more obvious: def data_to_table(d: Iterable[Mapping[str, float]], *, sort: bool = False, reversed: bool = False) -> Table: ... @dataclass class Stream: converter: data_to_table | None def add_converter(self, converter: data_to_table) -> None: self.converter = converter This solves the following problems with the `(P, Q) -> R` proposal: - how should this look like for "runtime" Python - how should we teach this - how can we express callables with complex signatures One disadvantage of this is that now arguments HAVE TO be named which raises questions: - should they be considered at type checking time? - how to express "I don't care"? To this I say: - yes, they should be considered at runtime (because kwargs have to be anyway) - ...unless they begin with an underscore This still leaves a minor problem that you can't have more than one argument literally named `_` so you'd have to do `_1`, `_2`, and so on. I don't think this is a big problem. In fact, forcing users to name callable arguments can be added as a fourth advantage to this design: making the annotations maximally informative to the human reader. The only remaining disadvantage that can't be addressed is that you can't create an *inline* callable type this way. I don't think this is a deal breaker as neither TypedDicts, Protocols, nor for this matter any PlainOldClasses can be defined inline inside a type annotation. - Ł
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