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How to compare values in two Pandas Dataframes?

  • Last Updated : 10 Jul, 2020
Geek Week

Let’s discuss how to compare values in the Pandas dataframe. Here are the steps for comparing values in two pandas Dataframes:

Step 1 Dataframe Creation: The dataframes for the two datasets can be created using the following code:




import pandas as pd
  
  
# elements of first dataset
first_Set = {'Prod_1': ['Laptop', 'Mobile Phone'
                        'Desktop', 'LED'],
             'Price_1': [25000, 8000, 20000, 35000]
                   }
  
# creation of Dataframe 1
df1 = pd.DataFrame(first_Set, columns = ['Prod_1', 'Price_1'])
print(df1)
  
# elements of second dataset
second_Set = {'Prod_2': ['Laptop', 'Mobile Phone',
                         'Desktop', 'LED'],
              'Price_2': [25000, 10000, 15000, 30000]  
                    }
  
# creation of Dataframe 2
df2 = pd.DataFrame(second_Set, columns = ['Prod_2', 'Price_2'])
print (df2)

Output:

pandas-comapre-value-2

pandas-comapre-value-2



Step 2 Comparison of values: You need to import numpy for the successful execution of this step. Here is the general template to perform the comparison:

df1[‘new column for the comparison results’] = np.where(condition, ‘value if true’, ‘value if false’)

Example: After execution of this code, the new column with the name Price_Matching will be formed under df1. Columns result will be displayed according to the following conditions:

  • If Price_1 is equal to Price_2, then assign the value of True
  • Otherwise, assign the value of False.




# add the Price2 column from 
# df2 to df1
df1['Price_2'] = df2['Price_2'
  
# create new column in df1 to 
# check if prices match
df1['Price_Matching'] = np.where(df1['Price_1'] == df2['Price_2'],
                                 'True', 'False')  
df1

Output:

pandas-comapre-value-3

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