fixed the premature newted mainloop(). in 'def ChangeToNewtMiscMainLoop(self, n=0)' after the print statement add self.master.wait_window( self ) that should keep us in the newterd mainloop until the foreign script destroy()s itself. Just like expected. I also got rid of the self.master.lift(),(duh!), in my Update method. I also cancel the self.master.after(...) when my apps cleanup code. With this done. You can quit your app before other running 'newtered' scripts and everybody stays happy (I think).