Pandas - dataframe groupby - how to get sum of multiple columns

Question

This should be an easy one, but somehow I couldn\'t find a solution that works.

I have a pandas dataframe which looks like this:

index col1   col2            


        

Answer 1

Another generic solution is

df.groupby(['col1','col2']).agg({'col3':'sum','col4':'sum'}).reset_index()

This will give you the required output.

UPDATED (June 2020): Introduced in Pandas 0.25.0, Pandas has added new groupby behavior “named aggregation” and tuples, for naming the output columns when applying multiple aggregation functions to specific columns.

df.groupby(
     ['col1','col2']
 ).agg(
     sum_col3 = ('col3','sum'),
     sum_col4     = ('col4','sum'),
 ).reset_index()

Refer to Link for detailed description.