game.py

import sys, pygame
pygame.init()

clock = pygame.time.Clock()
size = width, height = 640, 480
speed = [0,0]
black = 0, 0, 0
quitting_time = 0

screen = pygame.display.set_mode(size)

ball = pygame.image.load("ball.png")
ballrect = ball.get_rect()

while not quitting_time:
    clock.tick(60)
    speed = [0,0]
    for event in pygame.event.get():
        if event.type == pygame.KEYDOWN:
            if event.key == pygame.K_LEFT:    speed[0] = -10
            elif event.key == pygame.K_RIGHT: speed[0] = 10
            elif event.key == pygame.K_DOWN:  speed[1] = 10
            elif event.key == pygame.K_UP:    speed[1] = -10
    ballrect = ballrect.move(speed) # the important part
    screen.fill(black)
    screen.blit(ball, ballrect)
    pygame.display.flip()

pygame.quit()
sys.exit(0)