Get group id back into pandas dataframe

Question

For dataframe

In [2]: df = pd.DataFrame({\'Name\': [\'foo\', \'bar\'] * 3,
   ...:                    \'Rank\': np.random.randint(0,3,6),
   ...:                     


        

Answer 1

The correct solution is to use grouper.label_info:

df["GroupId"] = df.groupby(["Name", "Rank"]).grouper.label_info

It automatically associates each row in the df dataframe to the corresponding group label.