How to add rows with conditions together

Question

raw_data = {'id': [1,1,1,2,2,2,3,3,3],'v': [2,3,4,3,2,4,6,5,4]}
df = pd.DataFrame(raw_data, columns = ['id','v'])

I want to add "v" together if the "id" is the same. It should look like that:

       id  v
       1   9  
       2   9  
       3   15  

I tried something like:

for i in range(1, max(df_tracks["id"])+1):
    if df_tracks["id"] == i:
        pass

But it looks pretty wrong.

Answer 1

You can use groupby to achieve this:

In [5]: df.groupby("id", as_index=False).sum()
Out[5]: 
   id   v
0   1   9
1   2   9
2   3  15