How to add a second bouncing ball to the window?

Question

I have coded an animation (in python) for a beach ball to bounce around a screen. I now wish to add a second ball to the window, and when the two collide for them to bounce off each other.

So far, my attempts at this have been unsuccessful. Any ideas how to do this? The code I have so far is below.

import pygame

import sys

if __name__ =='__main__':

    ball_image = 'Beachball.jpg'
    bounce_sound = 'Thump.wav'
    width = 800
    height = 600
    background_colour = 0,0,0
    caption= 'Bouncing Ball animation'
    velocity = [1,1]
    pygame.init ()
    frame = pygame.display.set_mode ((width, height))
    pygame.display.set_caption (caption)
    ball= pygame.image.load (ball_image). convert()
    ball_boundary = ball.get_rect (center=(300,300))
    sound = pygame.mixer.Sound (bounce_sound)
    while True:
        for event in pygame.event.get():
            print event 
            if event.type == pygame.QUIT: sys.exit(0)
        if ball_boundary.left < 0 or ball_boundary.right > width:
            sound.play()
            velocity[0] = -1 * velocity[0]
        if ball_boundary.top < 0 or ball_boundary.bottom > height:
            sound.play()
            velocity[1] = -1 * velocity[1]

        ball_boundary = ball_boundary.move (velocity)
        frame.fill (background_colour)
        frame.blit (ball, ball_boundary)
        pygame.display.flip()

Answer 1

Here's a very basic restructure of your code. It could still be tidied up a lot, but it should show you how you can use instances of the class.

import pygame
import random
import sys

class Ball:
    def __init__(self,X,Y):
        self.velocity = [1,1]
        self.ball_image = pygame.image.load ('Beachball.jpg'). convert()
        self.ball_boundary = self.ball_image.get_rect (center=(X,Y))
        self.sound = pygame.mixer.Sound ('Thump.wav')

if __name__ =='__main__':
    width = 800
    height = 600
    background_colour = 0,0,0
    pygame.init()
    frame = pygame.display.set_mode((width, height))
    pygame.display.set_caption("Bouncing Ball animation")
    num_balls = 1000
    ball_list = []
    for i in range(num_balls):
        ball_list.append( Ball(random.randint(0, width),random.randint(0, height)) )
    while True:
        for event in pygame.event.get():
            print event 
            if event.type == pygame.QUIT:
                sys.exit(0)
        frame.fill (background_colour)
        for ball in ball_list:
            if ball.ball_boundary.left < 0 or ball.ball_boundary.right > width:
                ball.sound.play()
                ball.velocity[0] = -1 * ball.velocity[0]
            if ball.ball_boundary.top < 0 or ball.ball_boundary.bottom > height:
                ball.sound.play()
                ball.velocity[1] = -1 * ball.velocity[1]

            ball.ball_boundary = ball.ball_boundary.move (ball.velocity)
            frame.blit (ball.ball_image, ball.ball_boundary)
        pygame.display.flip()

Answer 2

You should probably create a class to represent your beachball. Then you'd instance as many as you like, and put the instances in a Python list.

You'd then go through that list on each frame, updating and rendering each.

You would need to include a method to test for collision against another ball (this is simple for circles). If a collision is detected, the balls involved should simulate a bounce away from each other.