itergroup_collisions: callback

import os
import sys
import math
import pygame as pg


def collidable(one,two):
    if one is two:
        return False
    else:
        return one.rect.colliderect(two.rect)


class Block(pg.sprite.Sprite):
    def __init__(self,color,speed,*rect):
        pg.sprite.Sprite.__init__(self)
        self.rect = pg.Rect(rect)
        self.image = pg.Surface(self.rect.size).convert()
        self.image.fill(color)
        self.speed = speed

    def update(self,screen_rect,group):
        self.rect.move_ip(self.speed,0)
        collision = pg.sprite.spritecollide(self,group,False,collidable)
        if collision or not screen_rect.contains(self.rect):
            self.speed *= -1


class Control(object):
    def __init__(self):
        os.environ["SDL_VIDEO_CENTERED"] = '1'
        pg.init()
        self.screen = pg.display.set_mode((500,270))
        self.screen_rect = self.screen.get_rect()
        self.clock = pg.time.Clock()
        self.done = False
        self.fps = 60.0
        self.blocks = self.make_blocks()

    def make_blocks(self):
        blocks = pg.sprite.Group()
        for i in range(30):
            y,x = divmod(i,6)
            rect = pg.Rect(x*55+100,y*55+20,10,10)
            speed = (1 if i%2 else -1)
            blocks.add(Block(pg.Color("green"),speed,rect))
        return blocks

    def event_loop(self):
        for event in pg.event.get():
            if event.type == pg.QUIT:
                self.done = True

    def main_loop(self):
        while not self.done:
            self.event_loop()
            self.blocks.update(self.screen_rect,self.blocks)
            self.screen.fill(0)
            self.blocks.draw(self.screen)
            pg.display.update()
            self.clock.tick(self.fps)


if __name__ == "__main__":
    run_it = Control()
    run_it.main_loop()
    pg.quit()
    sys.exit()