BUG: Unexpected result for Series.pow

[rohanjain101]

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

>>> k = pd.Series([2, None], dtype="int64[pyarrow]")
>>> k.pow(pd.NA, fill_value=3)
0    <NA>
1    <NA>
dtype: int64[pyarrow]
>>>

Issue Description

The documentation for Series.pow states that the fill_value will fill in missing values in 1 series, but result will be missing if the value is missing in both left and right for a given index. In this example, at index 0, the value is missing only in the right series, so I would have expected this to be filled in and produced a series with values [8, pd.NA]

Expected Behavior

I would expect pd.Series([8, pd.NA]) as the result.

Using a series with all null instead of a scalar also produces the expected result:

>>> s = pd.Series([2,None], dtype="int8[pyarrow]")
>>> k = pd.Series([None, None], dtype="int64[pyarrow]")
>>> s.pow(k, fill_value=3)
0       8
1    <NA>
dtype: int64[pyarrow]
>>>

Installed Versions

INSTALLED VERSIONS

commit : e86ed37
python : 3.11.2.final.0
python-bits : 64
OS : Windows
OS-release : 10
Version : 10.0.22621
machine : AMD64
processor : Intel64 Family 6 Model 85 Stepping 7, GenuineIntel
byteorder : little
LC_ALL : None
LANG : None
LOCALE : English_United States.1252

pandas : 2.1.1
numpy : 1.25.2
pytz : 2023.3
dateutil : 2.8.2
setuptools : 68.0.0
pip : 23.2.1
Cython : None
pytest : 7.0.1
hypothesis : None
sphinx : 4.2.0
blosc : None
feather : None
xlsxwriter : None
lxml.etree : None
html5lib : None
pymysql : None
psycopg2 : None
jinja2 : 3.1.2
IPython : 8.14.0
pandas_datareader : None
bs4 : 4.12.2
bottleneck : None
dataframe-api-compat: None
fastparquet : None
fsspec : None
gcsfs : None
matplotlib : None
numba : None
numexpr : None
odfpy : None
openpyxl : None
pandas_gbq : None
pyarrow : 13.0.0
pyreadstat : None
pyxlsb : None
s3fs : None
scipy : None
sqlalchemy : None
tables : None
tabulate : 0.9.0
xarray : None
xlrd : None
zstandard : None
tzdata : 2023.3
qtpy : None
pyqt5 : None

[rhshadrach]

Thanks for the report! Confirmed on main, further investigations and PRs to fix are welcome.

[gupta-paras]

Investigation: The possible cause of issue is in below function: https://github.com/pandas-dev/pandas/blob/main/pandas/core/ops/array_ops.py#L269

Here for dtype="int8[pyarrow]" type native pow is called, however for dtype="float", meth: _na_arithmetic_op is called, which handles special cases like : pow(1, NA) is 1, etc.

[hvsesha]

Hi
I tried this

import pandas as pd

s1 = pd.Series([1,None], dtype="int8[pyarrow]")
s2 = pd.Series([None, 2])

Expected result: [1, pd.NA]

actual_result = s1.pow(pd.NA, fill_value=3)

print(actual_result)