> import numpy as np
> import pandas as pd
> index=np.array([2,4,6,8,10])
> data=np.array([3,5,7,9,11])
> data=pd.DataFrame({'num':data},index=index)
> print(data)
  num
2   3
4   5
6   7
8   9
10  11
> select_index=index[index>5]
> print(select_index)
[ 6 8 10]
> data['num'].loc[select_index]
6   7
8   9
10  11
Name: num, dtype: int32
>

> data['num'].iloc[2:5] 
6   7 
8   9 
10  11 
Name: num, dtype: int32 
> data['num'].iloc[[2,3,4]] 
6   7 
8   9 
10  11 
Name: num, dtype: int32 
>