The File Renamer GUI is built with the Kivy GUI framework. It's a pretty simple app that takes in a few inputs (a prefix, a list of file extensions, and a folder) which it uses to rename all affected files (prefix_1.ext, prefix_2.ext, ...). More to come in this section in the future.
The app is packaged to an executable with PyInstaller so that it can be run with a double-click of the mouse. That way the end user doesn't need to install Python, create a virtual environment, update dependencies, run from the command line, etc. The app's code can be found at this GitHub repository. In the future I have plans to write blog posts on how to write Kivy applications and how to package applications with PyInstaller. Look for updates to this page with that info.