Pandas Show Group Sum On All Rows

Given the following dataframe: col_a | col_b_tosum b | 5 b | 5 b | 1 c | 6 c | 3 a | 2 a | 2 I would like to

Solution 1:

Use groupby with transform:

df['group_sum'] = df.groupby('col_a')['col_b_tosum'].transform('sum')

Output:

  col_a  col_b_tosum  group_sum
0b5111b5112b1113     c            694     c            395a246a24