Something

#/usr/bin/env python

import pygame, random
from pygame.locals import *

pygame.init( )

class Objects( pygame.sprite.Sprite ):
	def __init__( self, color, position ):
		pygame.sprite.Sprite.__init__( self )
		
		self.image = pygame.Surface( [ 15, 5 ] ).convert( )
		self.image.fill( color )
		self.rect    = self.image.get_rect( )
		self.rect.topleft   = position
		
class DrawBall( pygame.sprite.Sprite ):
    # changed
    def __init__ ( self, color, radius, velocity, screen_rects ):
        pygame.sprite.Sprite.__init__( self )

        self.image = pygame.Surface(( 2 * radius, 2 * radius )).convert( )
        self.rect    = self.image.get_rect( )
        self.image.set_colorkey(( 0, 0, 0 ))
        self.rect.center = ( 50, 50 )

        # changed
        self.velocity_x, self.velocity_y = velocity
        pygame.draw.circle( self.image, color, ( radius, radius ), radius )

        # changed
        self.screen_rect = screen_rects

    def UpdateBall( self ):
        # changed whole method
        if self.rect.right >= self.screen_rect.right or self.rect.left <= 0:
            self.velocity_x = -self.velocity_x
        if self.rect.bottom >= self.screen_rect.bottom:
            self.velocity_y = -self.velocity_y
        #if self.rect.right >= 200 -1 or self.rect.left <= 0:  velocity_x = - velocity_x

        self.rect.move_ip( self.velocity_x, self.velocity_y )

	
_screen_ = pygame.display.set_mode( [ 200, 200 ] )
_scrRect  = _screen_.get_rect( )

velocityX, velocityY =  random.randint( 1, 5 ), random.randint( 1, 5 )

objgroup =pygame.sprite.Group( )

#changed
_ball = DrawBall( [ 255, 0, 0 ], 5, (velocityX, velocityY), _scrRect)

for colors, pos in [ ( [ 255, 0, 0 ], [ 0, 5 ] ), ( [ 0, 255, 0 ], [ 15, 5 ] ),  ( [ 0, 0, 255 ], [ 30, 5 ] ) ]:
	objgroup.add( Objects( colors, pos ))

_loop_ = True

while pygame.event.poll( ).type != pygame.KEYDOWN: 
	pygame.time.delay( 30 )
	
	_screen_.fill(( 0, 0, 0 ))
	
	for b in objgroup.sprites( ): _screen_.blit( b.image, b.rect )
	
	_ball.UpdateBall()                             # changed
	_screen_.blit( _ball.image, _ball.rect )
	
	pygame.display.update( )

pygame.quit()