How do i make an enemy gradually follow the player in Pygame?

I have tried making a game and everything has been running smoothly until I tried to make a simple enemy AI. All I need it to do is gradually follow the player and I have tried doing it this way but it pauses the entire game.

        keys_pressed = pygame.key.get_pressed()
        if keys_pressed[pygame.K_w]:
            plr.y -= 3
            moveEnemy(emy, plr)
        if keys_pressed[pygame.K_s]:
            plr.y += 3
            moveEnemy(emy, plr)


        draw_window(plr, emy)
    pygame.quit()

def moveEnemy(emy, plr):
    while emy.y != plr.y:
        time.sleep(.25)
        emy.y -= (emy.y - plr.y) - 2

Does anyone know a better way I can do this?