join

import pandas as pd

df1 = pd.DataFrame({'A': [1, 2], 'B': [3, 4]}, index=['x', 'y'])
df2 = pd.DataFrame({'A': [5, 6], 'C': [7, 8]}, index=['x', 'y'])

# Left join with drop=False
result = df1.join(df2.set_index('A', drop=False), 
                 how='left',  # 명시적으로 left join 지정
                 lsuffix='_left', 
                 rsuffix='_right')

print(result)