from tkinter import Tk
from tkinter import Menu
 
counter = 0
 
def update():
    global counter
    counter = counter + 1
    menu.entryconfig(0, label=str(counter))
 
gyoker = Tk()
 
menusav = Menu(gyoker)
menu = Menu(menusav, tearoff=0, postcommand=update)
menu.add_command(label=str(counter))
menu.add_command(label="Kilépés", command=gyoker.quit)
menusav.add_cascade(label="Teszt", menu=menu)
 
gyoker.config(menu=menusav)
 
gyoker.mainloop()