While it is true that Tkinter uses old-style classes, this limitation can be overcome by additionally deriving the subclass Application from object (using Python multiple inheritance):
import Tkinter as tk
class Application(tk.Frame, object):
def __init__(self, master):
super(Application, self).__init__(master)
self.grid()
def main():
root = tk.Tk()
root.geometry('200x150')
app = Application(root)
root.mainloop()
main()
This will work so long as the Tkinter class doesn't attempt any behaviour which requires being an old-style class to work (which I highly doubt it would). I tested the example above with Python 2.7.7 without any issues.
This work around was suggested here. This behaviour is also included by default in Python 3 (referenced in link).
