Pandas DataFrame diff() Method

Preparation

Before any data manipulation can occur, two (2) new libraries will require installation.

• The Pandas library enables access to/from a DataFrame.
• The NumPy library supports multi-dimensional arrays and matrices in addition to a collection of mathematical functions.

To install these libraries, navigate to an IDE terminal. At the command prompt ($), execute the code below. For the terminal used in this example, the command prompt is a dollar sign ($). Your terminal prompt may be different.

$ pip install pandas

Hit the <Enter> key on the keyboard to start the installation process.

$ pip install numpy

Hit the <Enter> key on the keyboard to start the installation process.

If the installations were successful, a message displays in the terminal indicating the same.

Feel free to view the PyCharm installation guide for the required libraries.

• How to Install Pandas on PyCharm
• How to Install NumPy on PyCharm

Add the following code to the top of each code snippet. This snippet will allow the code in this article to run error-free.

import pandas as pd
import numpy as np 

DataFrame diff()

The diff() method calculates the difference between a DataFrame element compared with another element in the same DataFrame. The default is the element in the previous row.

The syntax for this method is as follows:

DataFrame.diff(periods=1, axis=0)

Code – Example 1

This example reflects the difference in regard to the previous row.

df_teams = pd.DataFrame({'Bruins':  [4, 5, 9],
                         'Oilers':   [3, 6, 10],
                         'Leafs':    [2, 7, 11],
                         'Flames': [1, 8, 12]})

result = df_teams.diff()
print(result)

• Line [1] creates a DataFrame from a Dictionary of Lists and saves it to df_teams.
• Line [2] uses the diff() method to determine the difference from the previous row and saves it to the result variable.
• Line [3] outputs the result to the terminal.

Output

Code – Example 2

This example reflects the difference in regard to the previous column.

df_teams = pd.DataFrame({'Bruins':   [4, 5, 9],
                         'Oilers':   [3, 6, 10],
                         'Leafs':    [2, 7, 11],
                         'Flames':   [1, 8, 12]})

result = df_teams.diff(axis=1)
print(result)

• Line [1] creates a DataFrame from a Dictionary of Lists and saves it to df_teams.
• Line [2] uses the diff() method to determine the difference from the previous column and saves it to the result variable.
• Line [3] outputs the result to the terminal.

Output

Code – Example 3

This example reflects the difference in regard to the previous rows.

df_teams = pd.DataFrame({'Bruins':   [4, 5, 9],
                         'Oilers':   [3, 6, 10],
                         'Leafs':    [2, 7, 11],
                         'Flames':   [1, 8, 12]})

result = df_teams.diff(periods=1)
print(result)

• Line [1] creates a DataFrame from a Dictionary of Lists and saves it to df_teams.
• Line [2] uses the diff() method to determine the difference from the previous column and with periods set to 1 and saves to the result variable.
• Line [3] outputs the result to the terminal.

Output

More Pandas DataFrame Methods

Feel free to learn more about the previous and next pandas DataFrame methods (alphabetically) here:

Also, check out the full cheat sheet overview of all Pandas DataFrame methods.