BUG: Fix Series.str.contains with compiled regex on Arrow string dtype (#61942)

doc/source/whatsnew/v2.3.2

@@ -0,0 +1,11 @@
+.. _whatsnew_232:
+
+These are the changes in pandas 2.3.2. See :ref:`release` for a full changelog
+including other versions of pandas.
+
+{{ header }}
+
+Bug fixes
+^^^^^^^^^
+
+- Fixed ``Series.str.contains`` with compiled regex on Arrow string dtype, which now correctly delegates to the object-dtype implementation. (:issue:`61942`)

pandas/core/arrays/string_arrow.py

@@ -346,6 +346,8 @@ def _str_contains(
     ):
         if flags:
             return super()._str_contains(pat, case, flags, na, regex)
+        if isinstance(pat, re.Pattern):
+            pat = pat.pattern
 
         return ArrowStringArrayMixin._str_contains(self, pat, case, flags, na, regex)
 

pandas/tests/strings/test_strings.py

@@ -2,6 +2,7 @@
     datetime,
     timedelta,
 )
+import re
 
 import numpy as np
 import pytest
@@ -176,6 +177,16 @@ def test_empty_str_methods(any_string_dtype):
     tm.assert_series_equal(empty_str, empty.str.translate(table))
 
 
+@pytest.mark.parametrize("dtype", ["string[pyarrow]"])
+def test_str_contains_compiled_regex_arrow_dtype(dtype):
+    ser = Series(["foo", "bar", "baz"], dtype=dtype)
+    pat = re.compile("ba.")
+    result = ser.str.contains(pat)
+    assert str(result.dtype) == "bool[pyarrow]"
+    expected = Series([False, True, True], dtype="bool[pyarrow]")
+    tm.assert_series_equal(result, expected)
+
+
 @pytest.mark.parametrize(
     "method, expected",
     [