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

Use GroupBy.ngroup from pandas 0.20.2+:

df["GroupId"] = df.groupby(["Name", "Rank"]).ngroup()
print (df)
  Name  Rank       Val  GroupId
0  foo     2  0.451724        4
1  bar     0  0.944676        0
2  foo     0  0.822390        2
3  bar     2  0.063603        1
4  foo     1  0.938892        3
5  bar     2  0.332454        1