code sample for pandas-dev#43205

Author: simonjayhawkins

bisect/43205.py

@@ -0,0 +1,15 @@
+# Combination of groupby with dropna set to True and apply function not returning expected output #43205
+
+import numpy as np
+import pandas as pd
+
+print(pd.__version__)
+
+df = pd.DataFrame(
+    {"a": [1, 2, 3, 4, 5, 6, 7, 8, 9], "b": [1, np.nan, 1, np.nan, 2, 1, 2, np.nan, 1]}
+)
+
+df_again = df.groupby("b", dropna=False).apply(lambda x: x)
+print(df_again)
+
+pd.testing.assert_frame_equal(df, df_again)