Description
Pandas version checks
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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
pandas as pd
class MySeries(pd.Series):
pass
class MyDataFrame(pd.DataFrame):
@property
def _constructor(self):
return MyDataFrame
_constructor_sliced = MySeries
MySeries._constructor_expanddim = MyDataFrame
df = MyDataFrame({"a": reversed(range(10)), "b": list('aaaabbbccc')})
assert isinstance(df.groupby("b").agg({"a": "sum"}), MyDataFrame)Traceback
AssertionError Traceback (most recent call last)
<ipython-input-7-e355635bac0a> in <cell line: 14>()
12 df = MyDataFrame({"a": reversed(range(10)), "b": list('aaaabbbccc')})
13
---> 14 assert isinstance(df.groupby("b").agg({"a": "sum"}), MyDataFrame)
AssertionError:
Issue Description
The df.groupby().agg() operation does not preserve subclass type. See this StackOverflow question for more details.
Other relevant issues:
- groupby and resample methods do not preserve subclassed data structures #28330
- BUG: DataFrameSubClass.groupby() doesn't use methods of subclass #51757
Expected Behavior
Expected behavior is that df.groupby().agg() would be the same class type as df.
Installed Versions
INSTALLED VERSIONS
commit : d9cdd2e
python : 3.10.12.final.0
python-bits : 64
OS : Linux
OS-release : 6.1.85+
Version : #1 SMP PREEMPT_DYNAMIC Thu Jun 27 21:05:47 UTC 2024
machine : x86_64
processor : x86_64
byteorder : little
LC_ALL : en_US.UTF-8
LANG : en_US.UTF-8
LOCALE : en_US.UTF-8
pandas : 2.2.2
numpy : 1.26.4
pytz : 2024.1
dateutil : 2.8.2
setuptools : 71.0.4
pip : 24.1.2
Cython : 3.0.11
pytest : 7.4.4
hypothesis : None
sphinx : 5.0.2
blosc : None
feather : None
xlsxwriter : None
lxml.etree : 4.9.4
html5lib : 1.1
pymysql : None
psycopg2 : 2.9.9
jinja2 : 3.1.4
IPython : 7.34.0
pandas_datareader : 0.10.0
adbc-driver-postgresql: None
adbc-driver-sqlite : None
bs4 : 4.12.3
bottleneck : None
dataframe-api-compat : None
fastparquet : None
fsspec : 2024.6.1
gcsfs : 2024.6.1
matplotlib : 3.7.1
numba : 0.60.0
numexpr : 2.10.1
odfpy : None
openpyxl : 3.1.5
pandas_gbq : 0.23.1
pyarrow : 14.0.2
pyreadstat : None
python-calamine : None
pyxlsb : None
s3fs : None
scipy : 1.13.1
sqlalchemy : 2.0.32
tables : 3.8.0
tabulate : 0.9.0
xarray : 2024.6.0
xlrd : 2.0.1
zstandard : None
tzdata : 2024.1
qtpy : None
pyqt5 : None