The proposed examples look awesome, thanks! On Sun, Nov 29, 2020 at 7:27 PM Guido van Rossum <gu...@python.org> wrote:
> That's a fair criticism -- Protocols are usable for this, but the syntax > is hardly the most intuitive, and most people would never think of this > approach. > > I guess the alternative would be to duplicate the full syntax allowed in > the parameter list of a 'def' statement (with some tweaks perhaps), so the > following would all be valid types: > > (x: float, method: int|None = None) -> str > (*args: int, **kwds: int) -> int > (a: int, b: int, /) -> int > > As for tweaks, maybe we can change things so that (int, int) -> int is > equivalent to the latter (since this is presumably still a very common > case). The rule would be something like "if there's no /, a / is assumed at > the end", and also "in positional args, the syntax is [name ':'] type_expr > ['=' default_expr]." > > Gotta go, > > On Sun, Nov 29, 2020 at 12:02 AM Andrew Svetlov <andrew.svet...@gmail.com> > wrote: > >> On Sun, Nov 29, 2020 at 1:49 AM Guido van Rossum <gu...@python.org> >> wrote: >> >>> On Sat, Nov 28, 2020 at 9:32 AM Andrew Svetlov <andrew.svet...@gmail.com> >>> wrote: >>> >>>> I would see support of all argument kinds support in any proposal for a >>>> new callable: positional only args, named args, keyword-only, *args and >>>> **kwargs. >>>> The exact notation in probably less important than missing >>>> functionality. >>>> >>> >>> Hm, but using Protocol you can already express every callable type. We >>> could duplicate all of the complexity of 'def' parameter lists into the >>> type notation, but it would be very complex. So this requirement is at >>> least debatable (I'm not actually sure how I feel about it). >>> >>> >> >> Don't get me wrong please. I'm not the typing system developer (while use >> typing every day in my code). >> You can consider this email as end-user feedback. >> >> I have a lot of code that uses `Callable[]` annotation; it is a natural >> way of annotating any callable, isn't it. >> Sometimes `Callable` doesn't work. For example, I cannot annotate a >> function that accepts a keyword-only argument. >> >> Sure, I can use Protocol but it doesn't feel natural and requires more >> code lines, especially if the Protocol is used once or twice. >> Also, Protocol adds `self` to methods which looks at least confusing when >> I annotate plain callables which naturally don't belong to any class: >> >> class MyFunc(typing.Protocol): >> def __call__(self, /, arg: int) -> str: ... >> >> Moreover, I recall a pull request to only of my libraries that had >> something similar to: >> >> class MyProto(typing.Protocol): >> def __call__(self_, /, self: Class, arg: int) -> str: ... >> >> The protocol actually had two 'self': one fake self for protocol itself >> and another one if the *real* self. >> The PR was refactored to use a more *natural* style but my first reaction >> was eyeballs :) >> >> The last thing that is unclear for me is mixing protocols with ParamSpec >> from PEP-612. >> >> Sure, I can live with all the mentioned limitations and learn all the >> required tricks if we have a consensus that Callable should operate with >> positional unnamed arguments only; but allowing to write such things in a >> manner similar to that Python supports for function definitions already >> makes life easier. >> >> -- >> Thanks, >> Andrew Svetlov >> > > > -- > --Guido van Rossum (python.org/~guido) > *Pronouns: he/him **(why is my pronoun here?)* > <http://feministing.com/2015/02/03/how-using-they-as-a-singular-pronoun-can-change-the-world/> > -- Thanks, Andrew Svetlov
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