How to conditionally remove duplicates from a pandas dataframe

Question

Consider the following dataframe

import pandas as pd
df = pd.DataFrame({\'A\' : [1, 2, 3, 3, 4, 4, 5, 6, 7],
                   \'B\' : [\'a\',\'b\',\'c\',\'         


        

Answer 1

Or you can just using first(), by using the first , will give back the first notnull value, so the order of original input does not really matter.

df.groupby(['A','B']).first()

Out[180]: 
    Col_1  Col_2
A B             
1 a   NaN      2
2 b     A      2
3 c     A      3
4 d     B      3
5 e     B      4
6 f   NaN      4
7 g   NaN      5