TST: ensure groupby get by index value pandas-dev#33439

Author: sam-cohan

doc/source/whatsnew/v1.1.0.rst

@@ -750,6 +750,7 @@ Other
 - Bug in :meth:`DataFrame.__dir__` caused a segfault when using unicode surrogates in a column name (:issue:`25509`)
 - Bug in :meth:`DataFrame.plot.scatter` caused an error when plotting variable marker sizes (:issue:`32904`)
 - :class:`IntegerArray` now implements the ``sum`` operation (:issue:`33172`)
+- Added test for getting values by index value during groupby aggregation (:issue:`33439`)
 
 .. ---------------------------------------------------------------------------
 

pandas/tests/groupby/aggregate/test_aggregate.py

@@ -940,3 +940,11 @@ def test_agg_multiple_lambda(self):
             weight_min=pd.NamedAgg(column="weight", aggfunc=lambda x: np.min(x)),
         )
         tm.assert_frame_equal(result2, expected)
+
+
+def test_groupby_get_by_index():
+    # GH 33439
+    df = pd.DataFrame({"A": ["S", "W", "W"], "B": [1.0, 1.0, 2.0]})
+    res = df.groupby("A").agg({"B": lambda x: x.get(x.index[-1])})
+    expected = pd.DataFrame(dict(A=["S", "W"], B=[1.0, 2.0])).set_index("A")
+    pd.testing.assert_frame_equal(res, expected)