Hello, I need to create a new dataframe which has an index column created from three diffrent columns of the original dataframe.

• The original dataframe (data) is:

  data = pd.DataFrame ({'DATE': ['Jan', 'Feb', 'Aug', 'Sep'], 'D1': ['12', '21', '32', '45'], 'D2': ['18', '22', '56', '12'], 'D3': ['13', '31', '82', '63']},index=[0, 1, 2, 3])

And it looks like this:

  DATE  D1  D2  D3
0  Jan  12  18  13
1  Feb  21  22  31
2  Aug  32  56  82
3  Sep  45  12  63

• From this original dataframe my goal is to create a dataframe (data_ds), which has two indexes (DATE and Ds), and looks like this:

              Dvalues
  DATE Ds
  Jan  D1     12
       D2     18
       D3     13
  Feb  D1     21
       D2     22
       D3     31
  Aug  D1     32
       D2     56
       D3     82
  Sep  D1     45
       D2     12
       D3     63
  

I have tried the following code, but I don't get there:

import pandas as pd
import numpy as np

data = pd.DataFrame ({'DATE': ['Jan', 'Feb', 'Aug', 'Sep'],
                'D1': ['12', '21', '32', '45'],
                'D2': ['18', '22', '56', '12'],
                'D3': ['13', '31', '82', '63']},index=[0, 1, 2, 3])


data_d1 = data[['DATE','D1']].copy()
data_d1 = data_d1.set_index('DATE')

data_d2 = data[['DATE','D2']].copy()
data_d2 = data_d2.set_index('DATE')

data_d3 = data[['DATE','D3']].copy()
data_d3 = data_d3.set_index('DATE')

data_ds=pd.concat([data_d1,data_d2,data_d3])
datos_ds = data_ds.set_index('DATE',(D1,D2,D3)) 

Thank you