import pandas as pd
import numpy as np

df1 = pd.DataFrame(np.random.randint(10, size=(12, 3)),
                   columns=list('ABC'))
df2 = pd.DataFrame(np.random.randint(10, size=(10, 3)),
                   columns=list('DEF'))

df = pd.concat([df1, df2], axis=1)

print(df.nunique())