REGR: Series access with Index of tuples/frozenset

doc/source/whatsnew/v1.1.2.rst

@@ -21,7 +21,8 @@ Fixed regressions
 - Regression in :meth:`DataFrame.replace` where a ``TypeError`` would be raised when attempting to replace elements of type :class:`Interval` (:issue:`35931`)
 - Fix regression in pickle roundtrip of the ``closed`` attribute of :class:`IntervalIndex` (:issue:`35658`)
 - Fixed regression in :meth:`DataFrameGroupBy.agg` where a ``ValueError: buffer source array is read-only`` would be raised when the underlying array is read-only (:issue:`36014`)
--
+- 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

@@ -887,21 +887,20 @@ 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 not is_iterator(key) and is_hashable(key):
             # Otherwise index.get_value will raise InvalidIndexError
-            try:
-                result = self._get_value(key)
-
-                return result
+            if isinstance(self.index, MultiIndex):
+                try:
+                    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)
+                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)
+            else:
+                # No fallback for an Index
+                return self._get_value(key)
 
         if is_iterator(key):
             key = list(key)

pandas/tests/series/indexing/test_indexing.py

@@ -1,6 +1,7 @@
 """ test get/set & misc """
 
 from datetime import timedelta
+import re
 
 import numpy as np
 import pytest
@@ -942,3 +943,26 @@ 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
+    with pytest.raises(KeyError, match="('c',)"):
+        s[("c",)]
+
+
+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
+    with pytest.raises(KeyError, match=re.escape("frozenset({'c'})")):
+        s[frozenset("c")]