A GUI (graphical user interface) can be made with Python modules.There are lots of modules designed for that. One of the oldest ones is Tkinter, the standard graphical interface package.
Through the years more modern modules have come out: Qt and WxWidgets.
The PyQT module works on all desktop platforms (Windows, Mac, Linux). It has a modern look and PyQt5 is the current version. QT includes GUI widgets, network sockets, SQL databases, a multimedia framework and many cool things.
A simple PyQt application.
An older module to create GUI applications. It works on Microsoft Windows and Mac OS X. This module contains less widgets than QT. It contains the basic widgets like buttons, textbox, listview and labels. If you are looking for advanced widgets or unusual widgets, I recommend QT or WxPython.
Python Desktop Apps with Tkinter
This is an alternative to PyQT and Tkinter. The WxPython module uses a C++ library called WxWidgets. With this module you can create applications for Windows, Mac OS X, Linux. Applications have a native look on all platforms. Unlike PyQt, WxPython is not developed by a commercial enterprise.