BUG: error when summing string to `pa.large_string`-backed Series

[MarcoGorelli]

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
import pyarrow as pa

# This runs fine!
data = {'a': ['foo']}
df = pd.DataFrame({'a': ['foo']}, dtype=pd.ArrowDtype(pa.string()))
df['a'] + '-'

# But this raises!
df = pd.DataFrame({'a': ['foo']}, dtype=pd.ArrowDtype(pa.large_string()))
df['a'] + '-'

Issue Description

This raises

Traceback (most recent call last):
  File "/home/marcogorelli/scratch/.venv/lib/python3.12/site-packages/pandas/core/arrays/arrow/array.py", line 986, in _evaluate_op_method
    result = pc.binary_join_element_wise(self._pa_array, other, sep)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/marcogorelli/scratch/.venv/lib/python3.12/site-packages/pyarrow/compute.py", line 269, in wrapper
    return func.call(args, options, memory_pool)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "pyarrow/_compute.pyx", line 399, in pyarrow._compute.Function.call
  File "pyarrow/error.pxi", line 155, in pyarrow.lib.pyarrow_internal_check_status
  File "pyarrow/error.pxi", line 92, in pyarrow.lib.check_status
pyarrow.lib.ArrowNotImplementedError: Function 'binary_join_element_wise' has no kernel matching input types (large_string, string, large_string)

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/home/marcogorelli/scratch/t.py", line 11, in <module>
    df['a'] + '-'
    ~~~~~~~~^~~~~
  File "/home/marcogorelli/scratch/.venv/lib/python3.12/site-packages/pandas/core/ops/common.py", line 85, in new_method
    return method(self, other)
           ^^^^^^^^^^^^^^^^^^^
  File "/home/marcogorelli/scratch/.venv/lib/python3.12/site-packages/pandas/core/arraylike.py", line 190, in __add__
    return self._arith_method(other, operator.add)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/marcogorelli/scratch/.venv/lib/python3.12/site-packages/pandas/core/series.py", line 6751, in _arith_method
    return base.IndexOpsMixin._arith_method(self, other, op)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/marcogorelli/scratch/.venv/lib/python3.12/site-packages/pandas/core/base.py", line 1644, in _arith_method
    result = ops.arithmetic_op(lvalues, rvalues, op)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/marcogorelli/scratch/.venv/lib/python3.12/site-packages/pandas/core/ops/array_ops.py", line 279, in arithmetic_op
    res_values = op(left, right)
                 ^^^^^^^^^^^^^^^
  File "/home/marcogorelli/scratch/.venv/lib/python3.12/site-packages/pandas/core/ops/common.py", line 85, in new_method
    return method(self, other)
           ^^^^^^^^^^^^^^^^^^^
  File "/home/marcogorelli/scratch/.venv/lib/python3.12/site-packages/pandas/core/arraylike.py", line 190, in __add__
    return self._arith_method(other, operator.add)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/marcogorelli/scratch/.venv/lib/python3.12/site-packages/pandas/core/arrays/arrow/array.py", line 1079, in _arith_method
    result = self._evaluate_op_method(other, op, ARROW_ARITHMETIC_FUNCS)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/marcogorelli/scratch/.venv/lib/python3.12/site-packages/pandas/core/arrays/arrow/array.py", line 990, in _evaluate_op_method
    raise TypeError(
TypeError: operation 'add' not supported for dtype 'large_string[pyarrow]' with object of type <class 'str'>

Expected Behavior

no error

Installed Versions

Details

pd.s>>> pd.show_versions()

INSTALLED VERSIONS

commit : e04b26f
python : 3.12.5
python-bits : 64
OS : Linux
OS-release : 6.6.87.2-microsoft-standard-WSL2
Version : #1 SMP PREEMPT_DYNAMIC Thu Jun 5 18:30:46 UTC 2025
machine : x86_64
processor : x86_64
byteorder : little
LC_ALL : None
LANG : C.UTF-8
LOCALE : C.UTF-8

pandas : 3.0.1
numpy : 2.4.2
dateutil : 2.9.0.post0
pip : 25.0.1
Cython : 3.2.4
sphinx : None
IPython : 9.10.0
adbc-driver-postgresql: None
adbc-driver-sqlite : None
bs4 : 4.14.3
bottleneck : None
fastparquet : None
fsspec : 2025.10.0
html5lib : None
hypothesis : None
gcsfs : 2025.2.0
jinja2 : 3.1.6
lxml.etree : None
matplotlib : 3.10.7
numba : None
numexpr : None
odfpy : None
openpyxl : None
psycopg2 : None
pymysql : None
pyarrow : 22.0.0
pyiceberg : None
pyreadstat : None
pytest : None
python-calamine : None
pytz : 2025.2
pyxlsb : None
s3fs : None
scipy : 1.16.0
sqlalchemy : None
tables : None
tabulate : 0.9.0
xarray : None
xlrd : None
xlsxwriter : None
zstandard : None
qtpy : None
pyqt5 : None

[SKMahesh15]

Hey @MarcoGorelli, I would be happy to take up and work on this issue.

[SKMahesh15]

Hey @MarcoGorelli, I was able to reproduce the bug. This is expected Python behaviour because PyArrow does not support the add operation.
If the goal is no error.
Then the feature + should be implemented in the PyArrow library itself.

Happy to hear your thoughts on this.

[jorisvandenbossche]

@MarcoGorelli thanks for the report! It seems that the scalar doesn't get cast to the type of the array, but just inferred using pyarrow, so we end up with string scalar and large_string array in the operation. I would argue that this is also something that could be allowed on the pyarrow side, but until then we should fix that on the pandas side.

@SKMahesh15 the "add" operation is specifically supported in pandas, through the use of the binary_join_element_wise kernel from pyarrow (since pyarrow itself indeed does not support "add" for strings)