Time based loops

[Owenix]

Having a hard time figuring out how to make timeloops.

The goal is having a text flicker on screen every even number of seconds (2,4,6 etc..)
This is the code i have so far:

intro = True
        x = time.time()
        while intro:
            y = int(time.time() - x)
            if y % 2 == 0:
               message_to_screen(font2,"Keys",white,(width/4,height/2)) 
            else:
               x = time.time()
               win.blit(background,(0,0))

The problem is that the screen is just freezing when running this.
I tried also setting time.sleep(1) after the loop, not working and even if so it kinda ruins the other code.

* Text is appearing on screen, and blit deletes everything off the screen EXCEPT "Keys".
Help will be much appreciated :)