code sample for pandas-dev#45648

Author: simonjayhawkins

bisect/45648.py

@@ -0,0 +1,20 @@
+# BUG: groupby transform doesn't respect Series index anymore #45648
+
+import pandas as pd
+
+print(pd.__version__)
+
+df = pd.DataFrame(
+    {
+        "A": ["foo", "bar", "foo", "bar", "bar", "foo", "foo"],
+        "C": [2.1, 1.9, 3.6, 4.0, 1.9, 7.8, 2.8],
+    }
+)
+grp = df.groupby("A")["C"]
+
+# sort C within groups defined by A
+result = grp.transform(pd.Series.sort_values)
+print(result)
+
+expected = grp.transform(lambda x: x.sort_values().values)
+pd.testing.assert_series_equal(result, expected)