class start_window(tk.Frame):

    def __init__(self, parent=None):
        tk.Frame.__init__(self, parent)
tk.Frame.pack(self)
tk.Label(self, text='Test', width=30).pack()
if __name__ == '__main__':
    root = tk.Tk()
root.wm_title('This is my title')
start_window(root)
root.mainloop()
Изменить заголовок кадра Tkinter