Countdown timer in Pygame

On this page you will find what you are looking for http://www.pygame.org/docs/ref/time.html#pygame.time.get_ticks
You download ticks once before beginning the countdown (which can be a trigger in the game – the key event, whatever). For example:

start_ticks=pygame.time.get_ticks() #starter tick
while mainloop: # mainloop
    seconds=(pygame.time.get_ticks()-start_ticks)/1000 #calculate how many seconds
    if seconds>10: # if more than 10 seconds close the game
        break
    print (seconds) #print how many seconds