BUG: .idxmax returns legacy strings for pyarrow dataframes #56272
Description
Pandas version checks
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I have confirmed this bug exists on the latest version of pandas.
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I have confirmed this bug exists on the main branch of pandas.
Reproducible Example
import pandas as pd
import io
data = '''name,x,y
matt a,10,20
fred b,20,1
jeff c,2,3
lisa d,5,7
adam e,23,1'''
df = pd.read_csv(io.StringIO(data), engine='pyarrow', dtype_backend='pyarrow')
df.select_dtypes('number').idxmax(axis='columns') # I would expect the dtype to be a pyarrow string not objectIssue Description
I want to stay with pyarrow types unless I explicitly convert to legacy types. The .idxmax method will convert the column names to object types instead of using pyarrow.
Expected Behavior
I want pyarrow types if possible.
Installed Versions
Details
INSTALLED VERSIONS
commit : e86ed37
python : 3.10.13.final.0
python-bits : 64
OS : Darwin
OS-release : 21.6.0
Version : Darwin Kernel Version 21.6.0: Wed Aug 10 14:28:23 PDT 2022; root:xnu-8020.141.5~2/RELEASE_ARM64_T6000
machine : arm64
processor : arm
byteorder : little
LC_ALL : en_US.UTF-8
LANG : None
LOCALE : en_US.UTF-8
pandas : 2.1.1
numpy : 1.23.5
pytz : 2023.3
dateutil : 2.8.2
setuptools : 67.6.1
pip : 23.2.1
Cython : 3.0.4
pytest : 7.2.0
hypothesis : 6.81.2
sphinx : None
blosc : None
feather : None
xlsxwriter : 3.1.2
lxml.etree : 4.9.2
html5lib : 1.1
pymysql : None
psycopg2 : None
jinja2 : 3.1.2
IPython : 8.8.0
pandas_datareader : None
bs4 : 4.11.1
bottleneck : None
dataframe-api-compat: None
fastparquet : None
fsspec : 2023.3.0
gcsfs : None
matplotlib : 3.6.2
numba : 0.56.4
numexpr : 2.8.4
odfpy : None
openpyxl : 3.0.10
pandas_gbq : None
pyarrow : 13.0.0
pyreadstat : None
pyxlsb : None
s3fs : None
scipy : 1.10.0
sqlalchemy : 2.0.21
tables : None
tabulate : 0.9.0
xarray : None
xlrd : 2.0.1
zstandard : None
tzdata : 2023.3
qtpy : None
pyqt5 : None