How to Randomly Change Your Windows Wallpaper with Python and ctypes

Before starting, note that this article is intended for Windows users only.

It demonstrates how to change the desktop background in Python without installing external libraries, using the built‑in ctypes module to call the Windows API.

First, a simple class sets the wallpaper by calling SystemParametersInfoW with the path of an image file.

import ctypes

class Main:
    def __init__(self):
        path = 'c:/...'
        ctypes.windll.user32.SystemParametersInfoW(20, 0, path, 0)

application = Main()

To make the script more flexible, it obtains the script’s directory using os and sys, then walks a folder named backgrounds to collect all PNG, JPG, and JPEG files.

import os
import sys

os.path.abspath(os.path.dirname(sys.argv[0]))
# e.g. 'C:\Users\user'

The final version randomly selects one image from the collected list and sets it as the wallpaper.

import os
import sys
import ctypes
import random

class Main:
    def __init__(self):
        self.path = os.path.abspath(os.path.dirname(sys.argv[0]))
        for root, directories, files in os.walk(os.path.join(self.path, 'backgrounds')):
            self.backgrounds = [file.lower() for file in files if file.endswith(('.png', '.jpg', '.jpeg'))]

        ctypes.windll.user32.SystemParametersInfoW(
            20, 0,
            os.path.join(self.path, 'backgrounds', random.choice(self.backgrounds)),
            0)

application = Main()

Place any desired images in the backgrounds folder; each execution of the script will temporarily set a random image as the desktop wallpaper.

For automatic execution at startup, copy the script into the shell:startup folder (opened via Win+R → “shell:startup”), so it runs each time Windows starts.