Apply function to every row in a Pandas DataFrame

Last Updated : 17 May, 2021

Python is a great language for performing data analysis tasks. It provides with a huge amount of Classes and function which help in analyzing and manipulating data in an easier way.
One can use apply() function in order to apply function to every row in given dataframe. Let’s see the ways we can do this task.
Example #1:

Python3

# Import pandas package
import pandas as pd
 
# Function to add
def add(a, b, c):
    return a + b + c
 
def main():
     
    # create a dictionary with
    # three fields each
    data = {
            'A':[1, 2, 3],
            'B':[4, 5, 6],
            'C':[7, 8, 9] }
     
    # Convert the dictionary into DataFrame
    df = pd.DataFrame(data)
    print("Original DataFrame:\n", df)
     
    df['add'] = df.apply(lambda row : add(row['A'],
                     row['B'], row['C']), axis = 1)
  
    print('\nAfter Applying Function: ')
    # printing the new dataframe
    print(df)
  
if __name__ == '__main__':
    main()

Output:

Example #2:
You can use the numpy function as the parameters to the dataframe as well.

Python3

import pandas as pd
import numpy as np
  
def main():
     
    # create a dictionary with
    # five fields each
    data = {
            'A':[1, 2, 3],
            'B':[4, 5, 6],
            'C':[7, 8, 9] }
     
    # Convert the dictionary into DataFrame
    df = pd.DataFrame(data)
    print("Original DataFrame:\n", df)
     
    # applying function to each row in the dataframe
    # and storing result in a new column
    df['add'] = df.apply(np.sum, axis = 1)
  
    print('\nAfter Applying Function: ')
    # printing the new dataframe
    print(df)
  
if __name__ == '__main__':
    main()

Output:

Example #3: Normalising Data

Python3

# Import pandas package
import pandas as pd
 
def normalize(x, y):
    x_new = ((x - np.mean([x, y])) /
             (max(x, y) - min(x, y)))
     
    # print(x_new)
    return x_new
 
def main():
     
    # create a dictionary with three fields each
    data = {
        'X':[1, 2, 3],
        'Y':[45, 65, 89] }
     
    # Convert the dictionary into DataFrame
    df = pd.DataFrame(data)
    print("Original DataFrame:\n", df)
     
    df['X'] = df.apply(lambda row : normalize(row['X'],
                                  row['Y']), axis = 1)
  
    print('\nNormalized:')
    print(df)
  
if __name__ == '__main__':
    main()

Output:

Example #4: Generate range

Python3

import pandas as pd
import numpy as np
  
pd.options.mode.chained_assignment = None
 
# Function to generate range
def generate_range(n):
     
    # printing the range for eg:
    # input is 67 output is 60-70
    n = int(n)
     
    lower_limit = n//10 * 10
    upper_limit = lower_limit + 10
     
    return str(str(lower_limit) + '-' + str(upper_limit))
      
def replace(row):
    for i, item in enumerate(row):
         
        # updating the value of the row
        row[i] = generate_range(item)
    return row
          
  
def main():
    # create a dictionary with
    # three fields each
    data = {
            'A':[0, 2, 3],
            'B':[4, 15, 6],
            'C':[47, 8, 19] }
     
    # Convert the dictionary into DataFrame
    df = pd.DataFrame(data)
  
    print('Before applying function: ')
    print(df)
      
    # applying function to each row in
    # dataframe and storing result in a new column
    df = df.apply(lambda row : replace(row))
      
  
    print('After Applying Function: ')
    # printing the new dataframe
    print(df)
  
if __name__ == '__main__':
    main()

Output:

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