This is the code I used to get that ball bouncing around my screen. See if you can go through it and understand it. Then try making some changes.
import sys, pygame pygame.init() size = width, height = 320, 240 speed = [1, 1] black = 0, 0, 0 screen = pygame.display.set_mode(size) ball = pygame.image.load("ball.png") ballrect = ball.get_rect() while 1: for event in pygame.event.get(): if event.type == pygame.QUIT: pygame.quit() sys.exit() ballrect = ballrect.move(speed) pygame.time.delay(10) if ballrect.left < 0 or ballrect.right > width: speed[0] = -speed[0] if ballrect.top < 0 or ballrect.bottom > height: speed[1] = -speed[1] screen.fill(black) screen.blit(ball, ballrect) pygame.display.flip()