On Thu, 22 Apr 2021 at 11:21, Paul Moore <p.f.mo...@gmail.com> wrote:
>
> On Thu, 22 Apr 2021 at 11:06, Chris Angelico <ros...@gmail.com> wrote:
> >
> > Someone will likely correct me if this is inaccurate, but my
> > understanding is that that's exactly what you get if you just don't
> > give a type hint. The point of type hints is to give more information
> > to the type checker when it's unable to simply infer from usage and
> > context.
>
> Hmm, I sort of wondered about that as I wrote it. But in which case,
> what's the problem here? My understanding was that people were
> concerned that static typing was somehow in conflict with duck typing,
> but if the static checkers enforce the inferred duck type on untyped
> arguments, then that doesn't seem to be the case. Having said that, I
> thought that untyped arguments were treated as if they had a type of
> "Any", which means "don't type check".
Looks like it doesn't:
> cat .\test.py
def example(f) -> None:
f.close()
import sys
example(12)
example(sys.stdin)
PS 12:00 00:00.009 C:\Work\Scratch\typing
> mypy .\test.py
Success: no issues found in 1 source file
What I was after was something that gave an error on the first call,
but not on the second. Compare this:
> cat .\test.py
from typing import Protocol
class X(Protocol):
def close(self): ...
def example(f: X) -> None:
f.close()
import sys
example(12)
example(sys.stdin)
PS 12:03 00:00.015 C:\Work\Scratch\typing
> mypy .\test.py
test.py:10: error: Argument 1 to "example" has incompatible type
"int"; expected "X"
Found 1 error in 1 file (checked 1 source file)
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/54C6G2JLYYD6B37J5KVKPCKSQDCGLRKA/
Code of Conduct: http://python.org/psf/codeofconduct/
