class tkinter.tix.Tk(screenName=None, baseName=None, className='Tix')
Toplevel widget of Tix which represents mostly the main window of an application. It has an associated Tcl interpreter.
Classes in the tkinter.tix module subclasses the classes in the tkinter. The former imports the latter, so to use tkinter.tix with Tkinter, all you need to do is to import one module. In general, you can just import tkinter.tix, and replace the toplevel call to tkinter.Tk with tix.Tk:
from tkinter import