Threading

from tkinter import *

from time import sleep

from threading import Thread

win = Tk()

win.geometry("500x400")

ctr1 = 0

def func1():

  for i in range(10):

    global ctr1

    ctr1 += 1

    lbl1.config(text=str(ctr1))

    sleep(1)

lbl1 = Label(win);  lbl1.pack()

t1 = Thread(target=func1, args=())

t1.start()

ctr2 = 0

def func2():

  for i in range(10):

    global ctr2

    ctr2 -= 1

    lbl2.config(text=str(ctr2))

    sleep(1)

lbl2 = Label(win);  lbl2.pack()

t2 = Thread(target=func2, args=())

t2.start()

win.mainloop()