CLN: re-use invalid_comparison in Categorical comparisons (#36229)

Author: jbrockmendel

pandas/core/arrays/categorical.py

@@ -119,15 +119,7 @@ def func(self, other):
                     ret[mask] = False
                 return ret
             else:
-                if opname == "__eq__":
-                    return np.zeros(len(self), dtype=bool)
-                elif opname == "__ne__":
-                    return np.ones(len(self), dtype=bool)
-                else:
-                    raise TypeError(
-                        f"Cannot compare a Categorical for op {opname} with a "
-                        "scalar, which is not a category."
-                    )
+                return ops.invalid_comparison(self, other, op)
         else:
             # allow categorical vs object dtype array comparisons for equality
             # these are only positional comparisons

pandas/tests/arrays/categorical/test_operators.py

@@ -171,17 +171,14 @@ def test_comparison_with_unknown_scalars(self):
         # for unequal comps, but not for equal/not equal
         cat = Categorical([1, 2, 3], ordered=True)
 
-        msg = (
-            "Cannot compare a Categorical for op __{}__ with a scalar, "
-            "which is not a category"
-        )
-        with pytest.raises(TypeError, match=msg.format("lt")):
+        msg = "Invalid comparison between dtype=category and int"
+        with pytest.raises(TypeError, match=msg):
             cat < 4
-        with pytest.raises(TypeError, match=msg.format("gt")):
+        with pytest.raises(TypeError, match=msg):
             cat > 4
-        with pytest.raises(TypeError, match=msg.format("gt")):
+        with pytest.raises(TypeError, match=msg):
             4 < cat
-        with pytest.raises(TypeError, match=msg.format("lt")):
+        with pytest.raises(TypeError, match=msg):
             4 > cat
 
         tm.assert_numpy_array_equal(cat == 4, np.array([False, False, False]))

pandas/tests/series/test_arithmetic.py

@@ -501,7 +501,7 @@ def test_unequal_categorical_comparison_raises_type_error(self):
         # for unequal comps, but not for equal/not equal
         cat = Series(Categorical(list("abc"), ordered=True))
 
-        msg = "Cannot compare a Categorical for op.+with a scalar"
+        msg = "Invalid comparison between dtype=category and str"
         with pytest.raises(TypeError, match=msg):
             cat < "d"
         with pytest.raises(TypeError, match=msg):