Pygame Preloader [Simple]

try:
    import pygame, time
    from pygame.locals import *
    pygame.init()

    a = 1.0

    #Colors
    BLACK = ( 0, 0, 0)
    WHITE = (255, 255, 255)
    GREEN = (0, 255, 0)
    RED = ( 255, 0, 0)

    #screen
    size = (700, 500)
    screen = pygame.display.set_mode(size)

    #screen background color
    screen.fill(WHITE)
    pygame.display.update()

    #Font
    myfont = pygame.font.SysFont('Anton', 30)

    for i in range(100):
        screen.fill((255, 255, 255))
        textsurface = myfont.render(str(a) + ' %', False, BLACK)
        screen.blit(textsurface,(320,210))
        pygame.display.update()
        a = a + 1
        time.sleep(0.05)
except:
    print('===> A problem Occurred <===')
    print('===> Exiting <===')