Relatedly, this means that dict does not implement collections.abc.Mapping which does allow keyword arguments:

Interesting. I wonder if that's worth fixing (but I also wonder if this has been brought up before).

but I also wonder if this has been brought up before

Oh, I didn't see that there is! #124675...where I participated in the discussion 😅

Interesting. I wonder if that's worth fixing (but I also wonder if this has been brought up before).

I would like for it to be fixed, and I have commented on a related issue (#124675).

As for "brought up before" - I'm not sure here, but I found this comment in typeshed:

    # Positional-only in dict, but not in MutableMapping
    @overload  # type: ignore[override]
    def get(self, key: _KT, /) -> _VT | None: ...
    @overload

https://github.com/python/typeshed/blob/17408ee5381f866c100f5003119a7a1bf050b839/stdlib/builtins.pyi#L1125C1-L1128C14

and discussion around that at python/typeshed#6694.

Oh, I didn't see that there is! https://github.com/python/cpython/issues/124675...where I participated in the discussion 😅

FWIW when you asked I pasted my issue text into ChatGPT and asked "I want to write up this bug for CPython. Has any duplicate issue been brought up before?". It found me that issue!

Instead of the change proposed here, a note like the following would better reflect the status quo:

CPython implementation detail: All arguments to this method are positional-only.

You can pass key= and default= as keyword arguments in PyPy (see online interpreter).

You can pass key= and default= as keyword arguments in PyPy (see online interpreter).

That's arguably a PyPy implementation detail :)

I'm going to close this in favor of #128208, which documents this for setdefault as well. Based on the aforementioned issue, changing the behavior is still on the table, but only for 3.14, so documenting this for bugfix versions is a good first step.