Python Tkinter First Example

import tkinter as tk

def on_closing():

    root.destroy()

class MainWindow(tk.Tk):

    def __init__(self, *args, **kwargs):

        tk.Tk.__init__(self, *args, **kwargs)

root = MainWindow()

root.title('Main Window')

root.protocol("WM_DELETE_WINDOW", on_closing)

root.geometry('640x480')

root.mainloop()