Removed import pd in test_scalar, updated test comments, whatsnew

Author: rhshadrach

doc/source/whatsnew/v1.1.0.rst

@@ -303,6 +303,7 @@ Indexing
 - Bug in :meth:`Series.loc` and :meth:`DataFrame.loc` when indexing with an integer key on a object-dtype :class:`Index` that is not all-integers (:issue:`31905`)
 - Bug in :meth:`DataFrame.iloc.__setitem__` on a :class:`DataFrame` with duplicate columns incorrectly setting values for all matching columns (:issue:`15686`, :issue:`22036`)
 - Bug in :meth:`DataFrame.loc:` and :meth:`Series.loc` with a :class:`DatetimeIndex`, :class:`TimedeltaIndex`, or :class:`PeriodIndex` incorrectly allowing lookups of non-matching datetime-like dtypes (:issue:`32650`)
+- Bug in :meth:`Series.at` when used with a :class:`MultiIndex` would raise an exception on valid inputs (:issue:`26989)
 
 Missing
 ^^^^^^^

pandas/tests/indexing/test_scalar.py

@@ -4,7 +4,6 @@
 import numpy as np
 import pytest
 
-import pandas as pd
 from pandas import DataFrame, Series, Timedelta, Timestamp, date_range
 import pandas._testing as tm
 from pandas.tests.indexing.common import Base
@@ -306,28 +305,32 @@ def test_iat_dont_wrap_object_datetimelike():
 
 
 def test_tuple_indexed_series_at_get():
-    series = pd.Series([1, 2], index=[(1, 2), (3, 4)])
+    # GH 26989
+    # Series.at works with MultiIndex
+    series = Series([1, 2], index=[(1, 2), (3, 4)])
     assert series.at[1, 2] == 1
 
 
 def test_tuple_indexed_series_at_set():
-    series = pd.Series([1, 2], index=[(1, 2), (3, 4)])
+    # GH 26989
+    # Series.at works with MultiIndex
+    series = 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.at works with multiindex
-    series = pd.Series([1, 2], index=[[1, 2], [3, 4]])
+    # Series.at works with MultiIndex
+    series = 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.at works with multiindex
-    series = pd.Series([1, 2], index=[[1, 2], [3, 4]])
+    # Series.at works with MultiIndex
+    series = Series([1, 2], index=[[1, 2], [3, 4]])
     series.at[1, 3] = 3
     assert series.at[1, 3] == 3
     series.loc[1, 3] = 4