A simple moving ball

image_animation.py

import pygame, sys
from pygame.locals import *

pygame.init()

FPS = 60
fpsClock = pygame.time.Clock()

DISPLAYSURF = pygame.display.set_mode((400,300), 0, 32)
pygame.display.set_caption('Animation')

WHITE = (255, 255, 255)
ballImg = pygame.image.load('ball.jpg')
ballx = 10
bally = 10
direction = 'right'

while True:
    DISPLAYSURF.fill(WHITE)

    if direction == 'right':
        ballx += 5
        if ballx == 340:
            direction = 'down'
    elif direction == 'down':
        bally += 5
        if bally == 240:
            direction = 'left'
    elif direction == 'left':
        ballx -= 5
        if ballx == 10:
            direction = 'up'
    elif direction == 'up':
        bally -= 5
        if bally == 10:
            direction = 'right'

    DISPLAYSURF.blit(ballImg, (ballx, bally))

    for event in pygame.event.get():
        if event.type == QUIT:
            pygame.quit()
            sys.exit()

    pygame.display.update()
    fpsClock.tick(FPS)