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  • [x] I have confirmed this bug exists on the main branch of pandas.

Reproducible Example

import pandas as pd
import re
DATA = ["applep", "bananap", "Cherryp", "DATEp", "eGGpLANTp", "123p", "23.45p"]
s=pd.Series(DATA)
s.str.fullmatch(re.compile(r"applep"))
s.str.match(re.compile(r"applep"))
sa=pd.Series(DATA, dtype="string[pyarrow]")
sa.str.fullmatch(re.compile(r"applep"))
sa.str.match(re.compile(r"applep"))

Issue Description

with pyarrow strings, the last line fails with:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "C:\Condadirs\envs\pandasstubs311\Lib\site-packages\pandas\core\strings\accessor.py", line 140, in wrapper
    return func(self, *args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Condadirs\envs\pandasstubs311\Lib\site-packages\pandas\core\strings\accessor.py", line 1429, in fullmatch
    result = self._data.array._str_fullmatch(pat, case=case, flags=flags, na=na)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Condadirs\envs\pandasstubs311\Lib\site-packages\pandas\core\arrays\_arrow_string_mixins.py", line 320, in _str_fullmatch
    if not pat.endswith("$") or pat.endswith("\\$"):
           ^^^^^^^^^^^^
AttributeError: 're.Pattern' object has no attribute 'endswith'
>>> sa.str.match(re.compile(r"applep"))
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "C:\Condadirs\envs\pandasstubs311\Lib\site-packages\pandas\core\strings\accessor.py", line 140, in wrapper
    return func(self, *args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Condadirs\envs\pandasstubs311\Lib\site-packages\pandas\core\strings\accessor.py", line 1388, in match
    result = self._data.array._str_match(pat, case=case, flags=flags, na=na)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Condadirs\envs\pandasstubs311\Lib\site-packages\pandas\core\arrays\_arrow_string_mixins.py", line 309, in _str_match
    if not pat.startswith("^"):
           ^^^^^^^^^^^^^^
AttributeError: 're.Pattern' object has no attribute 'startswith'

Expected Behavior

No exception

Installed Versions

INSTALLED VERSIONS ------------------ commit : c888af6d0bb674932007623c0867e1fbd4bdc2c6 python : 3.11.9 python-bits : 64 OS : Windows OS-release : 10 Version : 10.0.26100 machine : AMD64 processor : Intel64 Family 6 Model 183 Stepping 1, GenuineIntel byteorder : little LC_ALL : None LANG : None LOCALE : English_United States.1252 pandas : 2.3.1 numpy : 2.3.1 pytz : 2024.1 dateutil : 2.9.0.post0 pip : 24.2 Cython : None sphinx : None IPython : None adbc-driver-postgresql: None adbc-driver-sqlite : None bs4 : 4.13.4 blosc : None bottleneck : 1.4.2 dataframe-api-compat : None fastparquet : None fsspec : None html5lib : 1.1 hypothesis : None gcsfs : None jinja2 : 3.1.6 lxml.etree : 6.0.0 matplotlib : 3.10.3 numba : None numexpr : 2.10.1 odfpy : None openpyxl : 3.1.5 pandas_gbq : None psycopg2 : None pymysql : None pyarrow : 20.0.0 pyreadstat : 1.3.0 pytest : 8.4.1 python-calamine : None pyxlsb : 1.0.10 s3fs : None scipy : 1.16.0 sqlalchemy : 2.0.41 tables : 3.10.1 tabulate : 0.9.0 xarray : 2025.6.1 xlrd : 2.0.2 xlsxwriter : 3.2.5 zstandard : None tzdata : 2025.2 qtpy : None pyqt5 : None

Comment From: khemkaran10

take

Comment From: jorisvandenbossche

FWIW, we don't actually document (or test, I think) that this is supported. But because pat is passed to re.compile(..) in

https://github.com/pandas-dev/pandas/blob/e4a03b6e47a8ef9cd045902916289cbc976d3d33/pandas/core/strings/object_array.py#L249-L259

this works (since re.compile accepts that).

Given this works currently, I think it is certainly a good idea to keep this working for the string dtype as well. But then probably also should update the typing and docs.