Pandas: Creating aggregated column in DataFrame

Question

With the DataFrame below as an example,

In [83]:
df = pd.DataFrame({\'A\':[1,1,2,2],\'B\':[1,2,1,2],\'values\':np.arange(10,30,5)})
df
Out[83]:
   A  B  val         


        

Answer 1

In [15]: def sum_col(df, col, new_col):
   ....:     df[new_col] = df[col].sum()
   ....:     return df

In [16]: df.groupby("A").apply(sum_col, 'values', 'sum_values_A')
Out[16]: 
   A  B  values  sum_values_A
0  1  1      10            25
1  1  2      15            25
2  2  1      20            45
3  2  2      25            45