Python pandas rank/sort based on another column that differs for each input

Question

I would like to come up with the 4th column below based on the first three:

user    job  time  Rank
A   print   1559   2
A   print   1540   2
A   edit    1520           


        

Answer 1

First, assign a new column which contains the minimum time for user-job pairs:

df['min_time'] = df.groupby(['user', 'job'])['time'].transform('min')

Then group by each user and rank them:

df.groupby('user')['min_time'].rank(method='dense').astype(int)
Out: 
0    2
1    2
2    1
3    1
4    3
5    2
6    2
7    2
8    1
9    1
Name: min_time, dtype: int64