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How to Merge Two DataFrames in Pandas based on Multiple Common Column

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by Abdul Rawoof A R dot icon Updated: Feb 1, 2023

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Pandas is a well-known Python toolkit for handling and analysing data. A DataFrame is one of the core data structures provided by pandas. A DataFrame is a two-dimensional, size-mutable, and heterogeneous tabular data structure. 


To merge two or more pandas DataFrames into a multi-index DataFrame, you can use the “pd.merge()” function. 

  • pd.merge(): The pd.merge() function in pandas is used to combine multiple DataFrames based on one or more common columns (keys) between them. It is similar to the SQL JOIN operation and can combine data from multiple tables into a single DataFrame.

 

Alternatively, you can use the “pd.concat()” function to concatenate the DataFrames along a specific axis, and then use the “.set_index()” method to create a multi-index. 

  • pd.concat(): The pd.concat() function in pandas is used to concatenate or combine multiple pandas objects such as DataFrames or Series along a specific axis. 
  • .set_index(): The .set_index() method in pandas is used to set one or more columns as the index of a DataFrame. 


You can look at the code below to know more about merging Pandas DataFrame on the multindex column. 

Fig : Preview of the output that you will get on running this code from your IDE.

Code

In this solution we're using Pandas library.

merging pandas dataframe on multyindex columns

PythondotLines of Code : 17dotLicense : Strong Copyleft (CC BY-SA 4.0)

Dependent Libraries : 
## sample data
df = pd.DataFrame({'inspector_name':['Addison, Michael','Addison, Michael','Ahmad, Muna I','Ahmad, Muna I','Anderson, Trevis'],
                   'compliance': [0.0,1.0,0.0,1.0,0.0],
                   'compliance_detail':[0.4312, 0.0340, 0.7314,0.052,0.1666]})

df = df.set_index(['inspector_name','compliance'])

## solution

df = df.unstack().dropna().reset_index()
df.columns = ['inspector_name','negative_complaince','positive_complaince']
df

    inspector_name  negative_complaince     positive_complaince
0   Addison, Michael       0.4312                  0.034
1   Ahmad, Muna I          0.7314                  0.052

Instructions

Follow the steps carefully to get the output easily.

  1. Install pandas on your IDE(Any of your favorite IDE).
  2. Copy the snippet using the 'copy' and paste it in your IDE.
  3. Add required dependencies and import them in Python file.
  4. Add print statement at end of the code(like 'print(df)' instead of 'df').
  5. Run the file to generate the output.


I hope you found this useful. I have added the link to dependent libraries, version information in the following sections.


I found this code snippet by searching for 'merging pandas dataframe on multiindex columns' in kandi. You can try any such use case!

Environment Tested

I tested this solution in the following versions. Be mindful of changes when working with other versions.

  1. The solution is created in PyCharm 2021.3.
  2. The solution is tested on Python 3.9.7.
  3. Pandas version-v1.5.2.


Using this solution, we are able to merge pandas dataframe on multiindex columns with simple steps. This process also facilities an easy way to use, hassle-free method to create a hands-on working version of code which would help us to merge pandas dataframe on multiindex columns.

Dependent Library

pandasby pandas-dev

Python doticonstar image 38689 doticonVersion:v2.0.2doticon
License: Permissive (BSD-3-Clause)

Flexible and powerful data analysis / manipulation library for Python, providing labeled data structures similar to R data.frame objects, statistical functions, and much more

Support
    Quality
      Security
        License
          Reuse

            pandasby pandas-dev

            Python doticon star image 38689 doticonVersion:v2.0.2doticon License: Permissive (BSD-3-Clause)

            Flexible and powerful data analysis / manipulation library for Python, providing labeled data structures similar to R data.frame objects, statistical functions, and much more
            Support
              Quality
                Security
                  License
                    Reuse

                      You can also search for any dependent libraries on kandi like 'pandas'.

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