对于 pandas 列中的每个唯一值，对其他列进行排序

Question

I have a pandas dataframe as follows.

id      name      order
104337  CCC       7.0
104337  BBB       8.0
104337  AAA       9.0
104341  EE        1.0
104341  DD        2.0

I would like to group it by id with reversing the order for each id as follows.

id      name.     order
104337  AAA        9.0
104337  BBB        8.0
104337  CCC        7.0                  
104341  DD         2.0
104341  EE         1.0

I have tried df.groupby('id').apply(f) but I am confused how to create f function for my desired output.

Answer 1

Let's try

out = (df.groupby('id', as_index=False)
       .apply(lambda g: g.sort_values('order', ascending=False))
       .reset_index(drop=True))

print(out)

       id name  order
0  104337  AAA    9.0
1  104337  BBB    8.0
2  104337  CCC    7.0
3  104341   DD    2.0
4  104341   EE    1.0

Answer 2

You can first do groupby.apply then do sort_values too.

df.groupby('id').apply(lambda x:x).sort_values('order', ascending=False)

       id name  order
2  104337  AAA    9.0
1  104337  BBB    8.0
0  104337  CCC    7.0
4  104341   DD    2.0
3  104341   EE    1.0

Answer 3

I have solved it I think using the following code.

df.sort_values(['order'],ascending=False).groupby('id').apply(lambda x: x['name'])