On Sat, 13 Feb 2021 at 07:11, Steven D'Aprano <st...@pearwood.info> wrote: > > On Fri, Feb 12, 2021 at 10:27:01AM +0000, Mark Shannon wrote: > > > It impairs readability, because it muddles the return type. > > The function in the example returns a bool. > > The annotation is also misleading as the annotation is on the return > > type, not on the parameter that is narrowed. > > > > At a glance, most programmers should be able to work out what > > > > def is_str_list(val: List[object]) -> bool: > > > > returns. > > > > But, > > > > def is_str_list(val: List[object]) -> TypeGuard[List[str]]: > > > > is likely to confuse and require careful reading. > > Type hints are for humans as well as type checkers. > > This! > > Without reading the PEP, how is anyone supposed to know that this > returns a bool?
I have to agree here. I'm not a frequent user of type hints yet, but I am starting to have to maintain code that has type hints, and from a maintenance perspective, I have to say that this would be really hard to deal with. If I saw this for the first time "in the wild", I'd have no idea what to do with it. Paul _______________________________________________ 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/43A7TU2VYDIGFP3THLDFFUWJGWSZSIEM/ Code of Conduct: http://python.org/psf/codeofconduct/
