Using an operator is an interesting idea, and we should probably call it out as an alternative in the PEP. It's not a substitute for the current PEP from the standpoint of typing-sig for a few reasons:
(A) We care that the syntax be forward-compatible with supporting named arguments, as outlined in the "Extended Syntax" section of Rejected Alternatives and I don't think an operator-based syntax would extend to that. (B) We like supporting `(**P) -> bool` and `(int, **P) -> bool` for PEP 612 ParamSpec and Concatenate; this makes it much easier to write types for decorators, which are a common use case. It would be tricky to do this using an arrow operator. (C) I'd hesitate to add a dunder method on the tuple type, for reasons already mentioned here as well as the fact that it would force us to write unary callables - which are the most common kind - as `(int,) >> bool` ------ Separate from the question of arrow types, I wonder if an arrow operator would be worthwhile; I don't think it would have to be just for typing. Discussion probably belongs in a separate thread and I'd be happy to kick one off, but it sounds like Steve has a potential use case and I've always found the use of `>>`, which feels very low-level because it has baggage as a bit-shift, in DSLs to be a little weird. Proposing an operator like `=>` or `|>` (my preference would be not to use `->`) might make sense. The DSLs I'm thinking of (coming from data science) are all, loosely speaking, about some kind of pipelining - dplython uses `>>` to mimic R's pipeline operator, which works well for certain data transformations - At least at one point airflow supported creating DAG links using `>>` to represent control flow - As far as I know Tensorflow doesn't currently use `>>`, but their curried API that would lend itself to this _______________________________________________ Python-Dev mailing list -- python-dev@python.org To unsubscribe send an email to python-dev-le...@python.org https://mail.python.org/mailman3/lists/python-dev.python.org/ Message archived at https://mail.python.org/archives/list/python-dev@python.org/message/NIYHXMFKLN5C47ZIHBF7M4KSFJLZFDMQ/ Code of Conduct: http://python.org/psf/codeofconduct/
