how to self compare a column for duplicate values pandas code example

Example 1: concatenate dataframes pandas without duplicates

>>> df1
   A  B
0  1  2
1  3  1
>>> df2
   A  B
0  5  6
1  3  1
>>> pandas.concat([df1,df2]).drop_duplicates().reset_index(drop=True)
   A  B
0  1  2
1  3  1
2  5  6

Example 2: python - show repeted values in a column

df = df[df.duplicated(subset=['val1','val2'], keep=False)]