Backport PR #48662 on branch 1.5.x (BUG: Series.getitem not falling back to positional for bool index)

doc/source/whatsnew/v1.5.1.rst

@@ -83,6 +83,7 @@ Fixed regressions
 
 Bug fixes
 ~~~~~~~~~
+- Bug in :meth:`Series.__getitem__` not falling back to positional for integer keys and boolean :class:`Index` (:issue:`48653`)
 - Bug in :meth:`DataFrame.to_hdf` raising ``AssertionError`` with boolean index (:issue:`48667`)
 - Bug in :meth:`DataFrame.pivot_table` raising unexpected ``FutureWarning`` when setting datetime column as index (:issue:`48683`)
 -

pandas/core/indexes/base.py

@@ -5971,7 +5971,7 @@ def _should_fallback_to_positional(self) -> bool:
         """
         Should an integer key be treated as positional?
         """
-        return not self.holds_integer() and not self.is_boolean()
+        return not self.holds_integer()
 
     def _get_values_for_loc(self, series: Series, loc, key):
         """

pandas/tests/series/indexing/test_getitem.py

@@ -201,6 +201,12 @@ def test_getitem_str_with_timedeltaindex(self):
         with pytest.raises(KeyError, match=msg):
             ser["50 days"]
 
+    def test_getitem_bool_index_positional(self):
+        # GH#48653
+        ser = Series({True: 1, False: 0})
+        result = ser[0]
+        assert result == 1
+
 
 class TestSeriesGetitemSlices:
     def test_getitem_partial_str_slice_with_datetimeindex(self):

pandas/tests/series/indexing/test_indexing.py

@@ -367,6 +367,13 @@ def test_loc_setitem_nested_data_enlargement():
     tm.assert_series_equal(ser, expected)
 
 
+def test_getitem_bool_int_key():
+    # GH#48653
+    ser = Series({True: 1, False: 0})
+    with pytest.raises(KeyError, match="0"):
+        ser.loc[0]
+
+
 class TestDeprecatedIndexers:
     @pytest.mark.parametrize("key", [{1}, {1: 1}])
     def test_getitem_dict_and_set_deprecated(self, key):