The standard GUI (Graphical User Interface) package is called Tkinter. By default, its included with the Microsoft Windows and Mac OS X install of Python.
It is sometimes called “one of the minor traditions of the Python world”. Tkinter is by no means not the only GUI package, alternative GUI packages such as PyQT and wxPython are commonly used.
Compared to PyQT and wxPython, Tkinter has only a small amount of widgets such as a Button, Label, Checkbutton, Radiobutton, Listbox, Scrollbox, Progressbar and a few others.
Tkinter Messagebox, one of the widgets of Tkinter.
A brief introduction to Tkinter.
Note: In Python 3.x, the package is named tkinter. Programs written for Python 2.x may be importing Tkinter instead.