I want to draw two types of images with pygame at 30fps or more.

import time
import sys, random
import pygame
from pygame.locals import*

defmain():
    pygame.init()
    screen=pygame.display.set_mode(960,540))
    pygame.display.set_caption("image")
    logoA=pygame.image.load("checkA.bmp")
    logoA=pygame.transform.scale(logoA, (960,540))
    logoB=pygame.image.load("checkB.bmp")
    logoB = pygame.transform.scale(logoB, (960,540))
    imageFrag = 0
    fps = 28

    screen=pygame.display.set_mode(960,540))
    pygame.display.set_caption("image")
    t1 = time.time()
    while True:
        fpsclock = pygame.time.Clock()
        fpsclock.tick (fps)
        screen.fill(0,0,0))
        if imageFrag == 0:
            screen.blit(logoA,(0,0))
            imageFrag=1
            print ("logoA")
        else:
            screen.blit(logoB,(0,0))
            imageFrag = 0
            print("logoB")
        pygame.display.update()
        for event in pygame.event.get():
            if event.type==KEYDOWN:
                if event.key==K_SPACE:
                    t2 = time.time()
                    print(t2-t1)
                    print(fpsclock.get_fps())
                    pygame.quit()
                    sys.exit()

if__name__=='__main__':
    main()