fc

Signed-off-by: Praateek <[email protected]>

Author: praateekmahajan

pandas/core/series.py

@@ -6034,7 +6034,7 @@ def _flex_method(self, other, op, *, level=None, fill_value=None, axis: Axis = 0
 
         if isinstance(other, Series):
             return self._binop(other, op, level=level, fill_value=fill_value)
-        elif isinstance(other, (np.ndarray, list, tuple)):
+        elif isinstance(other, (np.ndarray, list, tuple, ExtensionArray)):
             if len(other) != len(self):
                 raise ValueError("Lengths must be equal")
             other = self._constructor(other, self.index, copy=False)

pandas/tests/series/test_arithmetic.py

@@ -155,6 +155,41 @@ def _check_fill(meth, op, a, b, fill_value=0):
         # should accept axis=0 or axis='rows'
         op(a, b, axis=0)
 
+    def test_extarray_rhs_datetime_sub_with_fill_value(self):
+        # Ensure ExtensionArray (DatetimeArray) RHS is handled via array-like path
+        # and does not hit scalar isna branch.
+        left = Series(
+            [
+                pd.Timestamp("2025-08-20"),
+                pd.Timestamp("2025-08-21"),
+                pd.Timestamp("2025-08-22"),
+            ],
+            dtype=np.dtype("datetime64[ns]")
+        )
+        right = left._values  # DatetimeArray
+
+        result = left.sub(right, fill_value=left.iloc[0])
+        # result dtype may vary (e.g., seconds vs ns), build expected from result dtype
+        expected = Series(np.zeros(3, dtype=np.dtype("timedelta64[ns]")))
+        tm.assert_series_equal(result, expected)
+
+    def test_extarray_rhs_timedelta_sub_with_fill_value(self):
+        left = Series([Timedelta(days=1), Timedelta(days=2), Timedelta(days=3)], dtype=np.dtype("timedelta64[ns]"))
+        right = left._values  # TimedeltaArray
+
+        result = left.sub(right, fill_value=left.iloc[0])
+        expected = Series(np.zeros(3, dtype=np.dtype("timedelta64[ns]")))
+        tm.assert_series_equal(result, expected)
+
+    def test_extarray_rhs_period_eq_with_fill_value(self):
+        # Use equality to validate ExtensionArray RHS path for PeriodArray
+        left = Series(pd.period_range("2020Q1", periods=3, freq="Q"))
+        right = left._values  # PeriodArray
+
+        result = left.eq(right, fill_value=left.iloc[0])
+        expected = Series([True, True, True])
+        tm.assert_series_equal(result, expected)
+
 
 class TestSeriesArithmetic:
     # Some of these may end up in tests/arithmetic, but are not yet sorted
@@ -404,6 +439,15 @@ def test_comparison_flex_alignment(self, values, op):
         expected = Series(values, index=list("abcd"))
         tm.assert_series_equal(result, expected)
 
+    def test_extarray_rhs_categorical_eq_with_fill_value(self):
+        # Categorical RHS should be treated as array-like, not as scalar
+        left = Series(Categorical(["a", "b", "a"]))
+        right = left._values  # Categorical
+
+        result = left.eq(right, fill_value=left.iloc[0])
+        expected = Series([True, True, True])
+        tm.assert_series_equal(result, expected)
+
     @pytest.mark.parametrize(
         "values, op, fill_value",
         [