ball.py

import pygame
from random import randint

BLACK = (0, 0, 0)

class Ball(pygame.sprite.Sprite):
    #Ball Class

    def __init__(self, color, width, height):
        super().__init__()

        #initialize image
        self.image = pygame.Surface([width, height])
        self.image.fill(BLACK)
        self.image.set_colorkey(BLACK)

        # Draw Rectangle
        pygame.draw.rect(self.image, color, [0, 0, width, height])

        #velocty array [x,y]
        self.velocity = [randint(4,8),randint(-8,8)]

        #get rectangle
        self.rect = self.image.get_rect()

    def update(self):
        #update ball position with velocity
        self.rect.x += self.velocity[0]
        self.rect.y += self.velocity[1]

    def bounce(self):
        #bounce ball
        self.velocity[0] = -self.velocity[0]
        self.velocity[1] = randint(-8,8)