Tweaked comments, adjusted tests

 - Added test for a series with an index of tuples
 - Combined at/loc tests, agreeing with the style of other tests

Author: rhshadrach

pandas/core/indexing.py

@@ -2058,7 +2058,7 @@ def _convert_key(self, key, is_setter: bool = False):
         fallback)
         """
         # For series, unpacking key needs to result in the label.
-        # This is already the case for non-multiindex
+        # This is already the case for len(key) == 1; e.g. (1,)
         if isinstance(self.obj, ABCSeries) and len(key) > 1:
             key = (key,)
 

pandas/tests/indexing/test_scalar.py

@@ -305,27 +305,30 @@ def test_iat_dont_wrap_object_datetimelike():
         assert not isinstance(result, Timedelta)
 
 
-def test_multiindex_series_loc_get():
-    series = pd.Series([1, 2], index=[[1, 2], [3, 4]])
-    assert series.loc[1, 3] == 1
+def test_tuple_indexed_series_at_get():
+    series = pd.Series([1, 2], index=[(1, 2), (3, 4)])
+    assert series.at[1, 2] == 1
 
 
-def test_multiindex_series_loc_set():
-    series = pd.Series([1, 2], index=[[1, 2], [3, 4]])
-    series.loc[1, 3] = 3
-    assert series.loc[1, 3] == 3
+def test_tuple_indexed_series_at_set():
+    series = pd.Series([1, 2], index=[(1, 2), (3, 4)])
+    series.at[1, 2] = 3
+    assert series.at[1, 2] == 3
 
 
 def test_multiindex_series_at_get():
     # GH 26989
-    # Series with multiindex at getter raises TypeError
+    # series.at works with multiindex
     series = pd.Series([1, 2], index=[[1, 2], [3, 4]])
     assert series.at[1, 3] == 1
+    assert series.loc[1, 3] == 1
 
 
 def test_multiindex_series_at_set():
     # GH 26989
-    # Series with multiindex at setter raises ValueError
+    # series.at works with multiindex
     series = pd.Series([1, 2], index=[[1, 2], [3, 4]])
     series.at[1, 3] = 3
     assert series.at[1, 3] == 3
+    series.loc[1, 3] = 4
+    assert series.loc[1, 3] == 4