Adjustments to comments.

Author: DriesSchaumont

doc/source/whatsnew/v1.3.0.rst

@@ -642,7 +642,7 @@ Indexing
 - Bug in setting ``numpy.timedelta64`` values into an object-dtype :class:`Series` using a boolean indexer (:issue:`39488`)
 - Bug in setting numeric values into a into a boolean-dtypes :class:`Series` using ``at`` or ``iat`` failing to cast to object-dtype (:issue:`39582`)
 - Bug in :meth:`DataFrame.loc.__setitem__` when setting-with-expansion incorrectly raising when the index in the expanding axis contains duplicates (:issue:`40096`)
-- Bug in :meth:`DataFrame.loc` incorrectly allowing the lookup of boolean labels and slices (:issue:`20432`)
+- Bug in :meth:`DataFrame.loc` incorrectly matching non-boolean index elements (:issue:`20432`)
 
 Missing
 ^^^^^^^

pandas/core/indexing.py

@@ -966,12 +966,12 @@ def _validate_key(self, key, axis: int):
         # slice of integers (only if in the labels)
         # boolean not in slice and with boolean index
         if isinstance(key, bool) and not is_bool_dtype(self.obj.index):
-            raise KeyError("Boolean label can not be used without a boolean index")
+            raise KeyError(f"{key}: boolean label can not be used without a boolean index")
 
         if isinstance(key, slice) and (
             isinstance(key.start, bool) or isinstance(key.stop, bool)
         ):
-            raise TypeError("Boolean values can not be used in a slice")
+            raise TypeError(f"{key}: boolean values can not be used in a slice")
 
     def _has_valid_setitem_indexer(self, indexer) -> bool:
         return True

pandas/tests/indexing/test_loc.py

@@ -2117,23 +2117,25 @@ def test_loc_getitem_slice_columns_mixed_dtype(self):
 
 
 class TestLocBooleanLabelsAndSlices(Base):
-    def test_loc_bool_incompatible_index_raises(self, index, frame_or_series):
+    @pytest.mark.parametrize("bool_value", [True, False])
+    def test_loc_bool_incompatible_index_raises(self, index, frame_or_series, bool_value):
         # GH20432
-        message = "Boolean label can not be used without a boolean index"
+        message = f"{bool_value}: boolean label can not be used without a boolean index"
         if index.inferred_type != "boolean":
             obj = frame_or_series(index=index, dtype="object")
             with pytest.raises(KeyError, match=message):
-                obj.loc[True]
+                obj.loc[bool_value]
 
-    def test_loc_bool_should_not_raise(self, frame_or_series):
+    @pytest.mark.parametrize("bool_value", [True, False])
+    def test_loc_bool_should_not_raise(self, frame_or_series, bool_value):
         obj = frame_or_series(
             index=Index([True, False], dtype="boolean"), dtype="object"
         )
-        obj.loc[True]
+        obj.loc[bool_value]
 
     def test_loc_bool_slice_raises(self, index, frame_or_series):
         # GH20432
-        message = "Boolean values can not be used in a slice"
+        message = "slice\(True, False, None\): boolean values can not be used in a slice"
         obj = frame_or_series(index=index, dtype="object")
         with pytest.raises(TypeError, match=message):
             obj.loc[True:False]