`Series.rename_axis(None)` not accepted

[dpoznik]

Describe the bug
To remove the name of the index of a Series, one may call Series.rename_axis(None), however mypy does not recognize None as a valid argument.

To Reproduce
This code:

import pandas as pd

s1 = pd.Series([1, 2, 3], name="values").rename_axis("index")
s2 = s1.rename_axis(None)
print(f"s1\n{s1}\n\ns2\n{s2}\n\n")

elicits the expected output when run:

s1
index
0    1
1    2
2    3
Name: values, dtype: int64

s2
0    1
1    2
2    3
Name: values, dtype: int64

but mypy complains with:

foo.py:4: error: No overload variant of "rename_axis" of "Series" matches argument type "None"  [call-overload]
foo.py:4: note: Possible overload variants:
foo.py:4: note:     def [ListLike: (Sequence[Any], ndarray[Any, Any], Series[Any], Index[Any])] rename_axis(self, mapper: str | bytes | date | datetime | timedelta | <9 more items> = ..., index: str | bytes | date | datetime | timedelta | <11 more items> | None = ..., columns: str | bytes | date | datetime | timedelta | <11 more items> | None = ..., axis: Literal['index', 0] | None = ..., copy: bool = ..., *, inplace: Literal[True]) -> None
foo.py:4: note:     def [ListLike: (Sequence[Any], ndarray[Any, Any], Series[Any], Index[Any])] rename_axis(self, mapper: str | bytes | date | datetime | timedelta | <9 more items> = ..., index: str | bytes | date | datetime | timedelta | <11 more items> | None = ..., columns: str | bytes | date | datetime | timedelta | <11 more items> | None = ..., axis: Literal['index', 0] | None = ..., copy: bool = ..., inplace: Literal[False] = ...) -> Series[int]
Found 1 error in 1 file (checked 1 source file)

Please complete the following information:

• OS: macOS 14.7.1
• Python version: 3.12.7
• Mypy version: 1.13.0
• Pandas-stubs version: 2.2.3.241009
• Pandas version: 2.2.3

[loicdiridollou]

Hey @dpoznik ,

Thanks for the report! What you are seeing is correct, there exists no overload for passing None (although it is allowed by the pandas API https://pandas.pydata.org/docs/reference/api/pandas.Series.rename_axis.html#pandas.Series.rename_axis).
We should add an overload to pass None as mapper. Do you confirm @Dr-Irv ?

pandas-stubs/pandas-stubs/core/series.pyi

Lines 2067 to 2087 in 779aab6

	@overload
	def rename_axis(
	self,
	mapper: Scalar | ListLike = ...,
	index: Scalar | ListLike | Callable | dict | None = ...,
	columns: Scalar | ListLike | Callable | dict | None = ...,
	axis: AxisIndex | None = ...,
	copy: _bool = ...,
	*,
	inplace: Literal[True],
	) -> None: ...
	@overload
	def rename_axis(
	self,
	mapper: Scalar | ListLike = ...,
	index: Scalar | ListLike | Callable | dict | None = ...,
	columns: Scalar | ListLike | Callable | dict | None = ...,
	axis: AxisIndex | None = ...,
	copy: _bool = ...,
	inplace: Literal[False] = ...,
	) -> Self: ...

[Dr-Irv]

We should add an overload to pass None as mapper. Do you confirm @Dr-Irv ?

I don't think an overload is needed. Just need to add None as a possible argument to mapper .

I also think the asterisk needs to be moved to after mapper . In addition, for Series.rename_axis(), the columns argument should not be allowed and should be removed.

A change to allow None should also be made in frame.pyi to set the type of the mapper argument there.

PR with tests welcome.

[dpoznik]

Cool, thanks for confirming. I'd be happy to submit a PR with all of the above at some point in the next few days. Could you assign the issue to me to ensure against duplicated effort?

[loicdiridollou]

You got it @dpoznik ! Looking forward!