How to Merge Two Pandas DataFrames on Index

In this article, we will discuss how to merge two Pandas Dataframes on Index in Python.

Merge two Pandas DataFrames on Index using join() 

This join() method is used to join the Dataframe based on the index.

Python3

# import pandas module
import pandas as pd

# create student  dataframe
data1 = pd.DataFrame({'id': [1, 2, 3, 4],
                      'name': ['manoj', 'manoja', 'manoji', 'manij']},
                     index=['one', 'two', 'three', 'four'])


# create marks  dataframe
data2 = pd.DataFrame({'s_id': [1, 2, 3, 6, 7],
                      'marks': [98, 90, 78, 86, 78]},
                     index=['one', 'two', 'three', 'siz', 'seven'])

# join two dataframes
print(data1.join(data2))

Output:

Merge Two Pandas DataFrames on Index using merge()

This merge() method will merge the two Dataframes with matching indexes 

Python3

# import pandas module
import pandas as pd

# join two dataframes with merge
print(pd.merge(data1, data2, left_index=True, right_index=True))

Output:

Merge Two Pandas DataFrames on Index using concat()

We can concatenate two Dataframes by using concat() method by setting axis=1.

Python3

# import pandas module
import pandas as pd

# join two dataframes with concat
print(pd.concat([data1, data2], axis=1))

Output: