code sample for pandas-dev#46983

Author: simonjayhawkins

bisect/46983.py

@@ -0,0 +1,21 @@
+# BUG: Setting values on a multiindex df, via loc, does nothing on 1.4.x #46983
+
+import pandas as pd
+
+print(pd.__version__)
+
+index = pd.MultiIndex.from_tuples(
+    [("A", "a"), ("A", "b"), ("A", "c"), ("A", "d"), ("B", "a"), ("B", "b")]
+)
+df = pd.DataFrame(
+    [[10, 100], [20, 200], [30, 300], [40, 400], [50, 500], [60, 600]],
+    columns=["val1", "val2"],
+    index=index,
+)
+df.loc["A"]["val1"] = 1
+print(df)
+
+expected = pd.DataFrame(
+    {"val1": [1, 1, 1, 1, 50, 60], "val2": [100, 200, 300, 400, 500, 600]}, index=index
+)
+pd.testing.assert_frame_equal(df, expected)