Is there a easy way to do a group by in Python to aggregate a single column

I have a dataframe with fields as follow

I would like aggregate field_2 i.e:

I usually create a new dataframe by doing a groupby on the dataframe with the field I want and then merge back the grouped dataframe to the original one. Is there an easier way to do this?

>Solution :

Try this:

df['field_2_agg'] = df['field_2'].sum()

Output:

>>> df
  field_1  field_2  field_3  field_2_agg
0       A        2        4            7
1       B        5        7            7