How to use apply() In Python Pandas

Q: How to use apply() In Python Pandas

We can create a function specifically for subtracting the columns, by taking column data as arguments and then using the apply method to apply it to all the data points throughout the column.

Method 2: Defining a function

Method 4: Using the Assign method

Since the operation we want to perform is simple we can you can directly use the apply() method without explicitly defining a function. Provide the axis argument as 1 to access the columns.

Syntax:

s.apply(func, convert_dtype=True, args=())

Parameters:

func: .apply takes a function and applies it to all values of pandas series.

convert_dtype: Convert dtype as per the function’s operation.

args=(): Additional arguments to pass to function instead of series.

Return Type: Pandas Series after applied function/operation.

Example: Subtract two columns in Pandas Dataframe

Python3

import pandas as pd 
import numpy as np 
  
data = np.arange(0, 20).reshape(4, 5) 
  
  
df = pd.DataFrame(data, 
                  index=['Row 1', 'Row 2', 'Row 3', 'Row 4'], 
                  columns=['Column 1', 'Column 2', 'Column 3', 
                           'Column 4', 'Column 5']) 
  
  
df['diff_3_4'] = df.apply(lambda x: x['Column 3'] - x['Column 4'], axis=1) 
df 