pandas - get most recent value of a particular column indexed by another column (get maximum value of a particular column indexed by another column)

Question

I have the following dataframe:

   obj_id   data_date   value
0  4        2011-11-01  59500    
1  2        2011-10-01  35200 
2  4        2010-07-31  24860          


        

Answer 1

I like crewbum's answer, probably this is faster (sorry, didn't tested this yet, but i avoid sorting everything):

df.groupby('obj_id').agg(lambda df: df.values[df['data_date'].values.argmax()])

it uses numpys "argmax" function to find the rowindex in which the maximum appears.