Pandas: Group by a column that meets a condition

Question

I have a data set with three colums: rating , breed, and dog.

import pandas as pd
dogs = {\'breed\': [\'Chihuahua\', \'Chihuahua\', \'Dalmatian\', \'Sphynx\'         


        

Answer 1

An alternative solution is to make dog one of your grouper keys. Then filter by dog in a separate step. This is more efficient if you do not want to lose aggregated data for non-dogs.

res = df.groupby(['dog', 'breed'])['rating'].mean().reset_index()

print(res)

     dog      breed  rating
0  False     Sphynx     7.0
1   True  Chihuahua     8.5
2   True  Dalmatian    10.0

print(res[res['dog']])

    dog      breed  rating
1  True  Chihuahua     8.5
2  True  Dalmatian    10.0