merge on index pandas

1pd.merge(df1, df2, left_index=True, right_index=True)
2

1import pandas as pd
2df1 = pd.DataFrame({'lkey': ['foo', 'bar', 'baz', 'foo'],
3                    'value': [1, 2, 3, 5]})
4df2 = pd.DataFrame({'rkey': ['foo', 'bar', 'baz', 'foo'],
5                    'value': [5, 6, 7, 8]})
6df1.merge(df2, left_on='lkey', right_on='rkey')

1>>> df1.merge(df2, left_on='lkey', right_on='rkey')
2  lkey  value_x rkey  value_y
30  foo        1  foo        5
41  foo        1  foo        8
52  foo        5  foo        5
63  foo        5  foo        8
74  bar        2  bar        6
85  baz        3  baz        7
9