import pandas as pd

df1 = pd.DataFrame({ 'colA': [10, 20, 30],
                     'colB': [100, 200, 300]})

df2 = pd.DataFrame({ 'colA': [40, 20, 50],
                     'colB': [400, 200, 500]})

new_df = pd.concat([df1, df2]).drop_duplicates().reset_index(drop=True)
print(new_df)