BUG: ser.loc[range] = foo treating key as positional

Author: jbrockmendel

pandas/core/indexing.py

@@ -665,7 +665,8 @@ def _get_setitem_indexer(self, key):
                 return self._convert_tuple(key)
 
         if isinstance(key, range):
-            return list(key)
+            # test_loc_setitem_range_key
+            key = list(key)
 
         return self._convert_to_indexer(key, axis=0)
 

pandas/tests/indexing/test_loc.py

@@ -1555,6 +1555,19 @@ def test_loc_setitem_cast3(self):
         df.one = np.int8(7)
         assert df.dtypes.one == np.dtype(np.int8)
 
+    def test_loc_setitem_range_key(self, frame_or_series):
+        # don't treat range key as positional
+        obj = frame_or_series(range(5), index=[3, 4, 1, 0, 2])
+
+        values = [9, 10, 11]
+        if obj.ndim == 2:
+            values = [[9], [10], [11]]
+
+        obj.loc[range(3)] = values
+
+        expected = frame_or_series([0, 1, 10, 9, 11], index=obj.index)
+        tm.assert_equal(obj, expected)
+
 
 class TestLocWithEllipsis:
     @pytest.fixture(params=[tm.loc, tm.iloc])