SeriesGroupBy nlargest and aggregations grouping by list with as_index=False returns dataframe instead of series

[mvashishtha]

Pandas version checks

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• 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

import pandas as pd

df = pd.DataFrame({'A': [1, 1, 2, 1, 2], 'B': [5, 6, 7, 8, 9]})
print(df.groupby([1, 1, 2, 1, 2], as_index=False)['B'].nlargest())

Issue Description

SeriesGroupBy nlargest() returns a series in every other case I have tried, including as_index=True. In this case I get a dataframe with a new range index as the row index.

Expected Behavior

Should return a series as in the other cases

Installed Versions

/Users/maheshvashishtha/anaconda3/envs/modin-dev/lib/python3.8/site-packages/_distutils_hack/init.py:33: UserWarning: Setuptools is replacing distutils.
warnings.warn("Setuptools is replacing distutils.")

INSTALLED VERSIONS

commit : 965ceca
python : 3.8.16.final.0
python-bits : 64
OS : Darwin
OS-release : 22.5.0
Version : Darwin Kernel Version 22.5.0: Mon Apr 24 20:51:50 PDT 2023; root:xnu-8796.121.2~5/RELEASE_X86_64
machine : x86_64
processor : i386
byteorder : little
LC_ALL : None
LANG : en_US.UTF-8
LOCALE : en_US.UTF-8

pandas : 2.0.2
numpy : 1.24.3
pytz : 2023.3
dateutil : 2.8.2
setuptools : 66.0.0
pip : 23.0.1
Cython : 0.29.34
pytest : 7.3.1
hypothesis : None
sphinx : 7.0.0
blosc : None
feather : 0.4.1
xlsxwriter : None
lxml.etree : 4.9.2
html5lib : None
pymysql : None
psycopg2 : 2.9.6
jinja2 : 3.1.2
IPython : 8.12.1
pandas_datareader: None
bs4 : 4.12.2
bottleneck : None
brotli : 1.0.9
fastparquet : 2022.12.0
fsspec : 2023.4.0
gcsfs : None
matplotlib : 3.7.1
numba : None
numexpr : 2.8.4
odfpy : None
openpyxl : 3.0.10
pandas_gbq : 0.19.1
pyarrow : 11.0.0
pyreadstat : None
pyxlsb : None
s3fs : 2023.4.0
scipy : 1.10.1
snappy : None
sqlalchemy : 1.4.45
tables : 3.8.0
tabulate : None
xarray : 2023.1.0
xlrd : 2.0.1
zstandard : None
tzdata : 2023.3
qtpy : None
pyqt5 : None

[mvashishtha]

Note that aggregations behave the same way, e.g.

import pandas as pd

df = pd.DataFrame({'A': [1, 1, 2, 1, 2], 'B': [5, 6, 7, 8, 9]})
print(df.groupby([1, 1, 2, 1, 2], as_index=False)['B'].mean())

[rhshadrach]

This is happening because #49519. Once that deprecation is enforced, the mean example will be a DataFrame with two columns, the first being the grouping key [1, 2]. As nlargest should be a filter, as_index should have no impact.

[rhshadrach]

I think this is handled by #49519 and #53707; closing. @mvashishtha - let me know if you think there is something more.