import pandas as pd

'''

ref. https://pandas.pydata.org/pandas-docs/stable/merging.html

pd.merge(left, right, how='inner', on=None, left_on=None, right_on=None,

left_index=False, right_index=False, sort=True,

suffixes=('_x', '_y'), copy=True, indicator=False,

validate=None)

'''

if __name__ == "__main__":

df_1 = pd.DataFrame(

{

'id': [1, 2, 3],

'key': ['a', 'b', 'c'],

}

)

print('=== df_1 ===')

print(df_1)

df_2 = pd.DataFrame(

{

'key': ['b', 'c', 'd'],

'value': ['b_value', 'c_value', 'd_value'],

}

)

print('=== df_2 ===')

print(df_2)

# inner join

pd_inner_join = pd.merge(df_1, df_2, how='inner', on='key', sort=True)

print('=== inner_join ===')

print(pd_inner_join)

# left join

pd_left_join = pd.merge(df_1, df_2, how='left', on='key', sort=True)

print('=== left_join ===')

print(pd_left_join)

# right join

pd_right_join = pd.merge(df_1, df_2, how='right', on='key', sort=True)

print('=== right_join ===')

print(pd_right_join)

# outer join

pd_outer_join = pd.merge(df_1, df_2, how='outer', sort=True)

print('=== outer_join ===')

print(pd_outer_join)