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Join Pandas DataFrames matching by substring

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  • Difficulty Level : Expert
  • Last Updated : 07 Apr, 2021

Prerequisites: Pandas

In this article, we will learn how to join two Data Frames matching by substring with python. 

Functions used:

  • join(): joins all the elements in an iteration into a single string
  • lambda(): an anonymous method which is declared without a name and can accept any number of parameters
  • find(): gets the initial appearance of any requisite value
  • merge(): merges two dataframes

Approach

Follow the below steps to join two data frames matched by substring.

  • Create two DataFrames.
  • Join two dataframes using cartesian product
  • Join a duplicate column including equal values in all the DataFrames
  • Join the new column
  • At last, remove the added column in each DataFrame.
  • Then we need to add a new column to the Data frame. To do this we will use the “lambda” along with “find” functions where the output is greater than zero.
  • Now we print the joined data frames matched by substrings .

Below is the implementation.

Python3




import pandas as pd
  
  
dataFrame1 = pd.DataFrame([['PQR', 'B1'], ['QRS', 'B2'], ['RDE', 'B3']], 
                          columns=['work_name', 'tag_name'])
  
dataFrame2 = pd.DataFrame([['RR', 'T1'], ['QR', 'T2'], ['HG', 'T3'], 
                           ['PQ', 'T4']],
                          columns=['sub_work_name', 'extra_tag_value'])
  
dataFrame1['join'] = 1
dataFrame2['join'] = 1
  
dataFrameFull = dataFrame1.merge(
  dataFrame2, on='join').drop('join', axis=1)
  
dataFrame2.drop('join', axis=1, inplace=True)
  
dataFrameFull['match'] = dataFrameFull.apply(
    lambda x: x.work_name.find(x.sub_work_name), axis=1).ge(0)
  
print(dataFrameFull[dataFrameFull['match']])

Output:

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