Backport PR #36147: REGR: Series access with Index of tuples/frozenset (#36332)

Co-authored-by: Richard Shadrach <45562402+rhshadrach@users.noreply.github.com>

Author: meeseeksmachine

doc/source/whatsnew/v1.1.3.rst

@@ -14,6 +14,8 @@ including other versions of pandas.
 
 Fixed regressions
 ~~~~~~~~~~~~~~~~~
+- Fixed regression in :meth:`Series.__getitem__` incorrectly raising when the input was a tuple (:issue:`35534`)
+- Fixed regression in :meth:`Series.__getitem__` incorrectly raising when the input was a frozenset (:issue:`35747`)
 -
 
 .. ---------------------------------------------------------------------------

pandas/core/series.py

@@ -881,21 +881,19 @@ def __getitem__(self, key):
  elif key_is_scalar:
  return self._get_value(key)
 
- if (
- isinstance(key, tuple)
- and is_hashable(key)
- and isinstance(self.index, MultiIndex)
- ):
+ if is_hashable(key):
  # Otherwise index.get_value will raise InvalidIndexError
  try:
+ # For labels that don't resolve as scalars like tuples and frozensets
  result = self._get_value(key)
 
  return result
 
  except KeyError:
- # We still have the corner case where this tuple is a key
- # in the first level of our MultiIndex
- return self._get_values_tuple(key)
+ if isinstance(key, tuple) and isinstance(self.index, MultiIndex):
+ # We still have the corner case where a tuple is a key
+ # in the first level of our MultiIndex
+ return self._get_values_tuple(key)
 
  if is_iterator(key):
  key = list(key)
@@ -955,7 +953,7 @@ def _get_values_tuple(self, key):
  return result
 
  if not isinstance(self.index, MultiIndex):
- raise ValueError("Can only tuple-index with a MultiIndex")
+ raise ValueError("key of type tuple not found and not a MultiIndex")
 
  # If key is contained, would have returned by now
  indexer, new_index = self.index.get_loc_level(key)
@@ -1009,9 +1007,11 @@ def __setitem__(self, key, value):
  # GH#12862 adding an new key to the Series
  self.loc[key] = value
 
- except TypeError as e:
+ except TypeError as err:
  if isinstance(key, tuple) and not isinstance(self.index, MultiIndex):
- raise ValueError("Can only tuple-index with a MultiIndex") from e
+ raise ValueError(
+ "key of type tuple not found and not a MultiIndex"
+ ) from err
 
  if com.is_bool_indexer(key):
  key = check_bool_indexer(self.index, key)

pandas/tests/series/indexing/test_indexing.py

@@ -383,7 +383,7 @@ def test_2d_to_1d_assignment_raises():
 @pytest.mark.filterwarnings("ignore:Using a non-tuple:FutureWarning")
 def test_basic_getitem_setitem_corner(datetime_series):
  # invalid tuples, e.g. td.ts[:, None] vs. td.ts[:, 2]
- msg = "Can only tuple-index with a MultiIndex"
+ msg = "key of type tuple not found and not a MultiIndex"
  with pytest.raises(ValueError, match=msg):
  datetime_series[:, 2]
  with pytest.raises(ValueError, match=msg):
@@ -942,3 +942,22 @@ def assert_slices_equivalent(l_slc, i_slc):
  for key2 in [keystr2, box(keystr2)]:
  assert_slices_equivalent(SLC[key2:key:-1], SLC[13:8:-1])
  assert_slices_equivalent(SLC[key:key2:-1], SLC[0:0:-1])
+
+
+def test_tuple_index():
+ # GH 35534 - Selecting values when a Series has an Index of tuples
+ s = pd.Series([1, 2], index=[("a",), ("b",)])
+ assert s[("a",)] == 1
+ assert s[("b",)] == 2
+ s[("b",)] = 3
+ assert s[("b",)] == 3
+
+
+def test_frozenset_index():
+ # GH35747 - Selecting values when a Series has an Index of frozenset
+ idx0, idx1 = frozenset("a"), frozenset("b")
+ s = pd.Series([1, 2], index=[idx0, idx1])
+ assert s[idx0] == 1
+ assert s[idx1] == 2
+ s[idx1] = 3
+ assert s[idx1] == 3