Handle non object dtype series

pandas/core/indexing.py

@@ -2024,7 +2024,14 @@ def ravel(i):
  return ser.reindex(ax)._values
 
  elif is_scalar(indexer) and isinstance(self.obj, ABCSeries):
- return ser
+ if is_object_dtype(self.obj):
+ return ser
+ ax = self.obj._get_axis(0)
+
+ if ser.index.equals(ax):
+ return ser._values.copy()
+
+ return ser.reindex(ax)._values[[indexer]]
 
  elif is_scalar(indexer):
  ax = self.obj._get_axis(1)

pandas/tests/series/indexing/test_setitem.py

@@ -93,11 +93,20 @@ def test_setitem_negative_out_of_bounds(self):
  with pytest.raises(IndexError, match=msg):
  ser[-11] = "foo"
 
- def test_setitem_series(self):
+ @pytest.mark.parametrize("ser_index", [0, 1])
+ def test_setitem_series_object_dtype(self, ser_index):
  # GH#38303
- ser = Series(0, index=[0, 1, 2])
- ser[0] = Series([42])
- expected = Series([42, 0, 0])
+ ser = Series([0, 0], dtype="object")
+ ser.loc[0] = Series([42], index=[ser_index])
+ expected = Series([Series([42], index=[ser_index]), 0], dtype="object")
+ tm.assert_series_equal(ser, expected)
+
+ @pytest.mark.parametrize("index, exp_value", [(0, 42.0), (1, np.nan)])
+ def test_setitem_series(self, index, exp_value):
+ # GH#38303
+ ser = Series([0, 0])
+ ser.loc[0] = Series([42], index=[index])
+ expected = Series([exp_value, 0])
  tm.assert_series_equal(ser, expected)