python-pygame的触碰方法

#!/usr/bin/env python
# -*- coding:utf-8 -*- 
# Author: ss

import pygame
import sys
import random
import math


class Ball(pygame.sprite.Sprite):
    def __init__(self, image, position, speed, bg_size):
        pygame.sprite.Sprite.__init__(self)
        self.image = pygame.image.load(image).convert_alpha()
        self.rect = self.image.get_rect()
        self.rect.left, self.rect.right = position
        self.speed = speed
        self.width, self.height = bg_size[0], bg_size[1]

    def move(self):
        self.rect = self.rect.move(self.speed)

        if self.rect.right < 0:
            self.rect.left = self.width
        if self.rect.left > self.
            self.rect.right = 0
        if self.rect.bottom < 0:
            self.rect.top = self.height
        if self.rect.top > self.height:
            self.rect.bottom = 0

def collide_check(item,target):
    col_balls = []
    for each in target:
        distance = math.sqrt(math.pow((item.rect.center[0] - each.rect.center[0]), 2) + 
                             math.pow((item.rect.center[1] - each.rect.center[1]), 2))
        if distance <= (item.rect.width + each.rect.width) / 2:
            col_balls.append(each)
    return col_balls


def main():
    pygame.init()

    ball_image = 'gray_ball.png'
    bg_image = 'background.png'

    bg_size = width, height = 1024, 681
    screen = pygame.display.set_mode(bg_size)
    pygame.display.set_caption('我的滚动的球 -s.s')
    background = pygame.image.load(bg_image)#.convert_alpha

    balls = []


    for i in range(5):
        position = random.randint(0, width - 100), random.randint(0, height - 100)
        speed = [random.randint(-10, 10), random.randint(-10, 10)]
        ball = Ball(ball_image, position, speed, bg_size)
        while collide_check(ball,balls):
            ball.rect.left, ball.rect.right = random.randint(0, width - 100), random.randint(0, height - 100)
        balls.append(ball)


    clock = pygame.time.Clock()

    running = True

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

        screen.blit(background, (0, 0))

        for each in balls:
            each.move()
            screen.blit(each.image, each.rect)

        for i in range(5):
            item = balls.pop(i)
            if collide_check(item, balls):
                item.speed[0] = -item.speed[0]
                item.speed[1] = -item.speed[1]
            balls.insert(i, item)

        pygame.display.flip()

        clock.tick(50)


if __name__ == "__main__":
    main()