Pong game in Python

I'm writing a pong game in Python and I created classes for the game objects.

The top level class is Object, and Ball and Paddle inherit from it. And ComputerPaddle is a child class of Paddle.

```
# classes.py
# 3/19/2013

import pygame
import random

# Paddle properties
PADDLE_WIDTH = 25
PADDLE_HEIGHT = 100
PADDLE_COLOR = (0, 0, 0)
PADDLE_SPEED = 6

# Ball properties
BALL_RADIUS = 20
BALL_COLOR = (0, 0, 0)
BALL_INITIAL_VX = -5
BALL_INITIAL_VY = -5

# Base object class
class Object:

# Initializes the object with coordinates, size and color
def __init__(self, x, y, w, h, color):
self.x = x
self.y = y
self.w = w
self.h = h
self.vx = 0
self.vy = 0
self.color = color

# Updates object by moving it and checking if it's in screen range
def update(self, screenWidth, screenHeight):
self.x += self.vx
self.y += self.vy

if self.x screenWidth - self.w: self.x = screenWidth - self.w
if self.y > screenHeight - self.h: self.y = screenHeight - self.h

# Must be implemented by child classes
def draw(self, surface):
pass

# Returns whether object collides with another object (rectangular collision detection)
def collides(self, obj):
return self.y obj.y and self.x obj.x

# Called when object collides with anoher object, must be implemented by child classes
def onCollide(self, obj):
pass

# Paddle class
class Paddle(Object):

# Initializes Paddle object
def __init__(self, x, y):
super(Paddle, self).__init__(x, y, PADDLE_WIDTH, PADDLE_HEIGHT, PADDLE_COLOR)

# Draws paddle with a rectangle
def draw(self, surface):
pygame.draw.rect(surface, self.color, (self.x, self.y, self.w, self.h))

# Moves paddle up
def moveUp(self):
self.vy -= PADDLE_SPEED

# Moves paddle down
def moveDown(self):
self.vy = PADDLE_SPEED

# Stops moving the paddle
def stopMovin

Instead of using 4 different fields to keep track of your object's position and size, I suggest you just use a Rect:

def __init__(self, x, y, w, h, color):
        self.rect = Rect(x, y, w, h)
        self.vx = 0
        self.vy = 0
        self.color = color

This way, you can simplify your code a lot.

Example: Collision detection

def collides(self, obj):
        return self.y  obj.y and self.x  obj.x

just becomes:

def collides(self, obj):
    return self.rect.colliderect(obj.rect)

Example: movement and bounds checking

def update(self, screenWidth, screenHeight):
    self.x += self.vx
    self.y += self.vy

    if self.x  screenWidth - self.w: self.x = screenWidth - self.w
    if self.y > screenHeight - self.h: self.y = screenHeight - self.h

can be rewritten as:

def update(self, screenWidth, screenHeight):    
    self.rect.move_ip(self.vx, self.vy)
    self.rect.clamp_ip(Rect(0, 0, screenWidth, screenHeight)

Example: drawing

def draw(self, surface):
    pygame.draw.rect(surface, self.color, (self.x, self.y, self.w, self.h))

becomes

def draw(self, surface):
    pygame.draw.rect(surface, self.color, self.rect)

Also, I probably wouldn't name a class Object, since there's already the object class.

Otherwise, I think your code is fine so far.

StackExchange Code Review Q#24167, answer score: 6