pygame经典sprite精灵类

import cStringIO, base64
import pygame
from pygame.locals import *

class Ball(pygame.sprite.Sprite):
    def __init__(self, color, initial_position):
        pygame.sprite.Sprite.__init__(self)
        ball_file = cStringIO.StringIO(base64.decodestring(
"""iVBORw0KGgoAAAANSUhEUgAAABkAAAAZCAYAAADE6YVjAAAAGXRFWHRTb2Z0d2FyZQBBZG9iZSBJ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="""))
        self.image = pygame.image.load(ball_file, 'file').convert_alpha()
        self.rect = self.image.fill(color, None, BLEND_ADD)
        self.rect.topleft = initial_position

pygame.init()
# screen = pygame.display.set_mode([350, 350])

# ball = Ball((255, 0, 0), (100, 100))
# screen.blit(ball.image, ball.rect)
# pygame.display.update()
# while pygame.event.poll().type != KEYDOWN:
#     pygame.time.delay(10)
class MoveBall(Ball):
    def __init__(self, color, initial_position, speed, border):
        super(MoveBall, self).__init__(color, initial_position)
        self.speed = speed
        self.border = border
        self.update_time = 0

    def update(self, current_time):
        if self.update_time < current_time:
            if self.rect.left < 0 or self.rect.left > self.border[0] - self.rect.w:
                self.speed[0] *= -1
            if self.rect.top < 0 or self.rect.top > self.border[1] - self.rect.h:
                self.speed[1] *= -1

            self.rect.x, self.rect.y = self.rect.x + self.speed[0], self.rect.y + self.speed[1]
            self.update_time = current_time + 10

pygame.init()
screen = pygame.display.set_mode([350, 350])

balls = []
for color, location, speed in [([255, 0, 0], [50, 50], [2,4]),
                        ([0, 255, 0], [100, 100], [3,2]),
                        ([0, 0, 255], [150, 150], [4,3])]:
    balls.append(MoveBall(color, location, speed, (350, 350)))

while True:
    if pygame.event.poll().type == QUIT: break

    screen.fill((0,0,0,))
    current_time = pygame.time.get_ticks()
    for b in balls:
        b.update(current_time)
        screen.blit(b.image, b.rect)
    pygame.display.update()