Using PyGame, I get flickering things. Boxes, circles, text, it all flickers. I can reduce this by increasing the wait between my loop, but I though maybe I could eliminate it by drawing everything to screen at once, instead of doing everything individually. Here's a simple example of what happens to me:

    import pygame, time
    pygame.init()
    screen = pygame.display.set_mode((400, 300))
    loop = "yes"
    while loop=="yes":
        screen.fill((0, 0, 0), (0, 0, 400, 300))
        font = pygame.font.SysFont("calibri",40)
        text = font.render("TextA", True,(255,255,255))
        screen.blit(text,(0,0))
        pygame.display.update()

        font = pygame.font.SysFont("calibri",20)
        text = font.render("Begin", True,(255,255,255))
        screen.blit(text,(50,50))
        pygame.display.update()
        time.sleep(0.1)

The "Begin" button flickers for me. It could just be my slower computer, but is there a way to reduce or eliminate the flickers? In more complex things I'm working on, it gets really bad. Thanks!
You're updating your screen 2 times in a loop, one for drawing first text(TextA) and one for second text(Begin).
After your first update, only first text appears, so you can't see begin text between first update and second update. This causes flickering.
Update your screen after drawing everything. In your case, remove first pygame.display.update().
Update display all at one time PyGame