BUG: pd.Series.rename(..., inplace=True) returns a pd.Series and not nont

[loicdiridollou]

Pandas version checks

• I have checked that this issue has not already been reported.

• I have confirmed this bug exists on the latest version of pandas.

• I have confirmed this bug exists on the main branch of pandas.

Reproducible Example

In [1]: import pandas as pd

In [2]: pd.Series([1, 2, 3])
Out[2]:
0    1
1    2
2    3
dtype: int64

In [3]: pd.Series([1, 2, 3]).rename('A')
Out[3]:
0    1
1    2
2    3
Name: A, dtype: int64

In [4]: pd.Series([1, 2, 3]).rename('A', inplace=True). # should return None
Out[4]:
0    1
1    2
2    3
Name: A, dtype: int64

Issue Description

According to the documation, inplace operations should return None and only modify the object in place without doing a deepcopy.
However when running the rename operation on pd.Series with inplace=True the type of the returns is pd.Series and not None.
This seems to originate from quick look up in the _set_name operations that return and object no matter the value of inplace (cf

pandas/pandas/core/series.py

Lines 1835 to 1850 in 6bcd303

	def _set_name(
	self, name, inplace: bool = False, deep: bool | None = None
	) -> Series:
	"""
	Set the Series name.
	Parameters
	----------
	name : str
	inplace : bool
	Whether to modify `self` directly or return a copy.
	"""
	inplace = validate_bool_kwarg(inplace, "inplace")
	ser = self if inplace else self.copy(deep=False)
	ser.name = name
	return ser

).
And then the rename operation only returns the result of _set_name without distinguishing the inplace value.

Expected Behavior

The docs suggest that the return of the rename(..., inplace=True) should be None.

Installed Versions

INSTALLED VERSIONS

commit : 0691c5c
python : 3.13.1
python-bits : 64
OS : Darwin
OS-release : 24.3.0
Version : Darwin Kernel Version 24.3.0: Thu Jan 2 20:24:06 PST 2025; root:xnu-11215.81.4~3/RELEASE_ARM64_T8103
machine : arm64
processor : arm
byteorder : little
LC_ALL : None
LANG : en_US.UTF-8
LOCALE : en_US.UTF-8

pandas : 2.2.3
numpy : 2.1.3
pytz : 2024.2
dateutil : 2.9.0.post0
pip : 24.3.1
Cython : None
sphinx : None
IPython : 8.29.0
adbc-driver-postgresql: None
adbc-driver-sqlite : None
bs4 : None
blosc : None
bottleneck : None
dataframe-api-compat : None
fastparquet : None
fsspec : None
html5lib : None
hypothesis : None
gcsfs : None
jinja2 : None
lxml.etree : None
matplotlib : 3.9.2
numba : None
numexpr : None
odfpy : None
openpyxl : None
pandas_gbq : None
psycopg2 : None
pymysql : None
pyarrow : None
pyreadstat : None
pytest : 8.3.3
python-calamine : None
pyxlsb : None
s3fs : None
scipy : None
sqlalchemy : None
tables : None
tabulate : None
xarray : None
xlrd : None
xlsxwriter : None
zstandard : None
tzdata : 2024.2
qtpy : None
pyqt5 : None

[rhshadrach]

Thanks for the report. Currently this is an inconsistency, but we will eventually be changing this so that all inplace=True return the instance. In addition, the inplace argument will be removed from rename. So closing this issue.

Ref: #51466

[loicdiridollou]

Great thanks for the note @rhshadrach.
Are you interested in me changing the docs to reflect the new behavior? Happy to make a PR!
Will have the pandas-stubs adjusted accordingly when this comes out!

[rhshadrach]

@loicdiridollou - an update to the docs would be welcome!