My input is a dataframe :

import pandas as pd

df = pd.DataFrame({'ID': ['ID001', 'ID001', 'ID001', 'ID002'],
 'N1': [1, 1, 2, 1],
 'N2': [1, 2, 1, 3],
 'SUB_GROUP': [2, 2, 2, 1],
 'CHUNK': [2, 2, 2, 4]})

I’m trying to add some rows (blue ones in the image below) based on the values of the columns SUB_GROUP and CHUNK. For example for ID002, the dataframe has only one row N1=1 and N2=3 and since this id must have one subgroup with 4 units each, then we add 1/1, 1/2 and 1/4.

I was able to generate almost the new rows to add but can’t find a way to merge them in my df :

for id in df['ID'].unique():
    new_rows = []
    df1 = df.loc[df['ID'] == id]
    len_sub_group = df1['SUB_GROUP'].iat[0]
    len_chunk = df1['CHUNK'].iat[0]
    for list1 in [list(n) for n in df1[['N1', 'N2']].values]:
        list1 = list([tuple(list1)])
        new_rows = [(len_sub_group, i)
            for i in range(1, len_chunk + 1)
            if (len_sub_group, i) not in list1]

Do you guys have an idea to do that ?