import time

def countdown(n):
    while n > 0:
        print("T-minus", n)
        n -= 1
        time.sleep(5)

def countdown2(n):
    while n > 0:
        print("T-minus", n)
        n -= 1
        time.sleep(6)

from threading import Thread

t = Thread(target=countdown, args=(10, ))
t.start()
t2 = Thread(target=countdown2, args=(10, ))
t2.start()