Pandas version checks
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[x] I have checked that this issue has not already been reported.
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[x] 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 numpy as np
import pandas as pd
pd.Series(np.array([b""])).groupby(level=0).last()
Issue Description
when calling groupby on a frame or series containing bytes, an exception is raised:
AttributeError: 'numpy.dtypes.BytesDType' object has no attribute 'construct_array_type'
Expected Behavior
Normal groupby behaviour
Installed Versions
INSTALLED VERSIONS
------------------
commit : c888af6d0bb674932007623c0867e1fbd4bdc2c6
python : 3.13.5
python-bits : 64
OS : Linux
OS-release : 4.18.0-425.3.1.el8.x86_64
Version : #1 SMP Fri Sep 30 11:45:06 EDT 2022
machine : x86_64
processor : x86_64
byteorder : little
LC_ALL : None
LANG : en_US.UTF-8
LOCALE : en_US.UTF-8
pandas : 2.3.1
numpy : 2.3.2
pytz : 2025.2
dateutil : 2.9.0.post0
pip : 25.2
Cython : None
sphinx : None
IPython : None
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 : None
numba : None
numexpr : None
odfpy : None
openpyxl : None
pandas_gbq : None
psycopg2 : None
pymysql : None
pyarrow : None
pyreadstat : None
pytest : None
python-calamine : None
pyxlsb : None
s3fs : None
scipy : None
sqlalchemy : None
tables : None
tabulate : None
xarray : None
xlrd : None
xlsxwriter : None
zstandard : None
tzdata : 2025.2
qtpy : None
pyqt5 : None
Comment From: rhshadrach
Thanks for the report. pandas does not support NumPy byte arrays, only bytes objects stored in an object dtype array. This should error on Series construction, which is #60108. Closing as a duplicate.