Make index first row in group in pandas dataframe

Question

I was wondering if it were possible to make the first row of each group based on index, the name of that index. Suppose we have a df like this:

dic = {'index_col': ['a','a','a','b','b','b'],'col1': [1, 2, 3, 4, 5, 6]}
df = pd.DataFrame(dic).set_index('index_col')

Is it possible to transform the dataframe above to one that looks like the one below? What happened here is that the index has been reset, and for every group, the first row is the index name?

Answer 1

The result is a pandas.Series ;

df_list = []
for label , group in df.groupby('index_col'):
    df_list.append(pandas.concat([pandas.Series([label]), group['col1']]))

df_result = pandas.concat(df_list).reset_index(drop=True)

Output;

0    a
1    1
2    2
3    3
4    b
5    4
6    5
7    6
dtype: object

Call df_result.to_frame() if you want a data-frame.