Simple Guide to Python GUI: Using the Standard Tkinter Library

The focus of the book is on learning by example with many short Tkinter example programs. The book explains and demonstrates use of the of the available GUI widgets from Labels and Buttons, Frames, Menus, Radiobuttons, Checkbuttons, Scrollbars, Listboxes, Comboboxes and many more.
This volume also covers the newer Themed Tkinter Widgets and examples of how to use Styles that allow for a modern look and feel and includes additional widgets that are not present in the classic Tkinter.

Tkinter is a great GUI library for Python because it is a native library that comes with Python. It is also:
Easy to learn
The syntax of Tkinter is very similar to Python, so it is easy to learn for beginners.
Cross-platform
Tkinter applications can be run on Windows, macOS, and Linux.
Free and open source
Tkinter is free to use and modify, and the source code is available for anyone to view