from tkinter import*
import  time

tc = 5
def tempo(tc):
    while tc:
        mins, secs = divmod(tc, 60)
        timer = '{:02d}:{:02d}'.format(mins, secs)
        print(timer, end="\r")
        time.sleep(1)
        tc -= 1
    print("ouverture")

fenetre = Tk()
label = Label(fenetre, text=tempo(tc))
label.pack()
fenetre.mainloop()