code sample for pandas-dev#42659

Author: simonjayhawkins

bisect/42659.py

@@ -0,0 +1,22 @@
+# BUG:dataframe.groupby('some_column').timedelta.sum() results wrong when timedelta contains NaT (pandas=1.3.0) #42659
+
+import numpy as np
+import pandas as pd
+
+print(pd.__version__)
+
+df = pd.DataFrame(
+    {
+        "id": ["1624477460271-3908654213", "1624477460271-3908654213"],
+        "dt": [np.nan, pd.to_timedelta("0:0:2")],
+    }
+)
+result = df.groupby("id").dt.sum()
+print(result)
+
+expected = pd.Series(
+    [pd.to_timedelta("0:0:2")],
+    index=pd.Index(["1624477460271-3908654213"], name="id"),
+    name="dt",
+)
+pd.testing.assert_series_equal(result, expected)