Python: Pandas - Delete the first row by group

Question

I have the following large dataframe (df) that looks like this:

    ID     date        PRICE       
1   10001  19920103  14.500    
2   10001  1         


        

Answer 1

Old but still watched quite often: a much faster solution is nth(0) combined with drop duplicates:

def using_nth(df):
    to_del = df.groupby('ID',as_index=False).nth(0)
    return pd.concat([df,to_del]).drop_duplicates(keep=False)

In my system the times for unutbus setting are:

using_nth       : 0.43
using_apply_alt : 1.93
using_mask      : 2.11
using_apply     : 4.33