BUG: dot on Arrow Series produces a Numpy object result · Issue #61375 · pandas-dev/pandas (original) (raw)

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

import pandas as pd

series_result = pd.Series({"a": 1.0}, dtype="Float64").dot( pd.DataFrame({"col1": {"a": 2.0}, "col2": {"a": 3.0}}, dtype="Float64") ) series_result.dtype # is dtype('O')

series_result_2 = pd.Series({"a": 1.0}, dtype="float[pyarrow]").dot( pd.DataFrame({"col1": {"a": 2.0}, "col2": {"a": 3.0}}, dtype="float[pyarrow]") ) series_result_2.dtype # same, is dtype('O')

DataFrame.dot was already fixed

df_result = pd.DataFrame({"col1": {"a": 2.0}, "col2": {"a": 3.0}}, dtype="Float64").T.dot( pd.Series({"a": 1.0}, dtype="Float64") ) df_result.dtype # is Float64Dtype()

Issue Description

Series.dot with Arrow or nullable dtypes returns series result with numpy object dtype. This was reported in #53979 and fixed for DataFrames in #54025.

Possibly side notes: I believe the "real" issue here is that the implementation uses .values which returns a dtype=object array for the DataFrame. This seems directly related to #60038 and at least somewhat related to #60301 (which is also referenced in a comment on the former).

Expected Behavior

I would expect Series.dot to return the "best" common datatype for the input datatypes (in the examples, would expect the appropriate float dtype)

import pandas as pd

series_result = pd.Series({"a": 1.0}, dtype="Float64").dot( pd.DataFrame({"col1": {"a": 2.0}, "col2": {"a": 3.0}}, dtype="Float64") ) series_result.dtype # would expect Float64Dtype()

series_result_2 = pd.Series({"a": 1.0}, dtype="float[pyarrow]").dot( pd.DataFrame({"col1": {"a": 2.0}, "col2": {"a": 3.0}}, dtype="float[pyarrow]") ) series_result_2.dtype # would expect float[pyarrow]

Installed Versions

INSTALLED VERSIONS

commit : 0691c5c
python : 3.11.12
python-bits : 64
OS : Windows
OS-release : 10
Version : 10.0.19045
machine : AMD64
processor : Intel64 Family 6 Model 85 Stepping 7, GenuineIntel
byteorder : little
LC_ALL : None
LANG : None
LOCALE : English_United States.1252

pandas : 2.2.3
numpy : 2.2.5
pytz : 2025.2
dateutil : 2.9.0.post0
pip : 25.1
Cython : None
sphinx : 8.2.3
IPython : 9.2.0
adbc-driver-postgresql: None
adbc-driver-sqlite : None
bs4 : 4.13.4
blosc : None
bottleneck : None
dataframe-api-compat : None
fastparquet : None
fsspec : 2025.3.2
html5lib : None
hypothesis : None
gcsfs : None
jinja2 : 3.1.6
lxml.etree : None
matplotlib : 3.10.1
numba : 0.61.2
numexpr : 2.10.2
odfpy : None
openpyxl : 3.1.5
pandas_gbq : None
psycopg2 : 2.9.9
pymysql : None
pyarrow : 19.0.1
pyreadstat : None
pytest : 8.3.5
python-calamine : None
pyxlsb : None
s3fs : None
scipy : 1.15.2
sqlalchemy : 2.0.40
tables : 3.10.2
tabulate : None
xarray : None
xlrd : 2.0.1
xlsxwriter : None
zstandard : 0.23.0
tzdata : 2025.2
qtpy : None
pyqt5 : None