import os

import Tkinter

class MainWindow(Tkinter.Frame):
    def __init__(self, parent):
        super(MainWindow, self).__init__(parent)
       
        self.parent = parent
        self.grid(row=0, columns=0)
        etc...

application = Tkinter.Tk()
#path = os.path.join(os.path.dirname(__file__), "images/")
application.title("Testing")

window = MainWindow(application)
application.protocol("WM_DELETE_WINDOW", window.quit)
application.mainloop()

...
class MainWindow(Tkinter.Frame):
    def __init__(self, parent):
        #super(MainWindow, self).__init__(parent)
        Tkinter.Frame.__init__(self, parent)
...