BUG: fix .str.isdigit to honor unicode superscript for older pyarrow

Author: jorisvandenbossche

doc/source/whatsnew/v2.3.2.rst

@@ -22,7 +22,8 @@ become the default string dtype in pandas 3.0. See
 
 Bug fixes
 ^^^^^^^^^
--
+- Fix :meth:`~Series.str.isdigit` to correctly recognize unicode superscript
+  characters as digits for :class:`StringDtype` backed by PyArrow (:issue:`61466`)
 
 .. ---------------------------------------------------------------------------
 .. _whatsnew_232.contributors:

pandas/core/arrays/_arrow_string_mixins.py

@@ -15,6 +15,7 @@
     HAS_PYARROW,
     pa_version_under13p0,
     pa_version_under17p0,
+    pa_version_under21p0,
 )
 
 if HAS_PYARROW:
@@ -261,6 +262,12 @@ def _str_isdecimal(self):
         return self._convert_bool_result(result)
 
     def _str_isdigit(self):
+        if pa_version_under21p0:
+            # https://github.com/pandas-dev/pandas/issues/61466
+            res_list = self._apply_elementwise(str.isdigit)
+            return self._convert_bool_result(
+                pa.chunked_array(res_list, type=pa.bool_())
+            )
         result = pc.utf8_is_digit(self._pa_array)
         return self._convert_bool_result(result)
 

pandas/tests/strings/test_strings.py

@@ -240,8 +240,9 @@ def test_ismethods(method, expected, any_string_dtype):
 @pytest.mark.parametrize(
     "method, expected",
     [
-        ("isnumeric", [False, True, True, False, True, True, False]),
-        ("isdecimal", [False, True, False, False, False, True, False]),
+        ("isnumeric", [False, True, True, True, False, True, True, False]),
+        ("isdecimal", [False, True, False, False, False, False, True, False]),
+        ("isdigit", [False, True, True, False, False, False, True, False]),
     ],
 )
 def test_isnumeric_unicode(method, expected, any_string_dtype):
@@ -250,7 +251,7 @@ def test_isnumeric_unicode(method, expected, any_string_dtype):
     # 0x1378: ፸ ETHIOPIC NUMBER SEVENTY
     # 0xFF13: ３ Em 3  # noqa: RUF003
     ser = Series(
-        ["A", "3", "¼", "★", "፸", "３", "four"],  # noqa: RUF001
+        ["A", "3", "³", "¼", "★", "፸", "３", "four"],  # noqa: RUF001
         dtype=any_string_dtype,
     )
     expected_dtype = (