Wewnętrzne połączenie pandy na dwóch kolumnach
new_df = pd.merge(A_df, B_df, how='left', left_on=['A_c1','c2'], right_on = ['B_c1','c2'])
Hambo
new_df = pd.merge(A_df, B_df, how='left', left_on=['A_c1','c2'], right_on = ['B_c1','c2'])
df = pd.merge(left=df1, right=df2, on=['var_1', 'var_2'], how='inner']