df.merge left_on several columns code example

Example 1: pd merge on multiple columns

new_df = pd.merge(A_df, B_df,  how='left', left_on=['A_c1','c2'], right_on = ['B_c1','c2'])

Example 2: python inner join based on two columns

df  = pd.merge(left=df1, right=df2, on=['var_1', 'var_2'], how='inner']