```
df=pd.DataFrame({'col1':[25021,25002,8002,40211,2232,""]})

    col1    
0   25021    
1   25002
2   8002
3   40211
4   2232
5   

```

I would like to get the following, not too sure how to split based on last 3 digits into col3 and whatever preceding into col1

```
    col2   col3    
0   25     021       
1   25     002       
2   8      002      
3   40     211       
4   2      232 
5

```