Pong game in Pygame

Question

This is my first time trying OOP and I definitely made many stylistic mistakes. Please tell me how I should improve.

Controls:

• w and s for player 1
• ↑ and ↓ for player 2

The player with higher score has shorter paddle. Once the difference in score is bigger than 7, the game quits.

import pygame
import random
YELLOW = (255, 255, 100)
BLUE = (50, 50, 255)
RED = (255, 50, 50)
BLACK = (0, 0, 0)
WHITE = (255,255,255)
SCREEN_WIDTH = 800
SCREEN_HEIGHT = 600
PADDLE_HEIGHT = 100
done = False
class Ball(pygame.sprite.Sprite):
 def __init__(self, x, y, xspeed, yspeed):
 super().__init__()
 self.image = pygame.Surface((16,16))
 self.rect = self.image.get_rect()
 self.x = x
 self.y = y
 self.rect.x = x
 self.rect.y = y
 pygame.draw.circle(self.image,YELLOW,(8,8),8)
 self.speed_x = xspeed
 self.speed_y = yspeed
 self.deathcount_left = None
 self.deathcount_right = None
 self.walls = None
 self.index = 0
 def checkdeath(self):
 if self.rect.x<0:
 self.deathcount_left.plus()
 self.rect.x = self.x
 self.rect.y = self.y
 self.speed_x = random.randint(8,12)
 self.speed_y = random.randint(8,12)
 elif self.rect.x>SCREEN_WIDTH:
 self.deathcount_right.plus()
 self.rect.x = self.x
 self.rect.y = self.y
 self.speed_x = random.randint(10,12)
 self.speed_y = random.randint(10,12) 
 def update(self):
 self.checkdeath()
 self.rect.x += self.speed_x
 wall_hit_list = pygame.sprite.spritecollide(self, self.walls, False)
 if self.index == 1:
 self.rect.y+=self.speed_y
 self.index = 0
 else:
 if wall_hit_list:
 self.speed_x = -self.speed_x
 self.rect.y += self.speed_y
 else:
 self.rect.y += self.speed_y
 wall_hit_list = pygame.sprite.spritecollide(self, self.walls, False)
 if wall_hit_list:
 self.speed_y = -self.speed_y
 self.index=1
class Wall(pygame.sprite.Sprite):
 def __init__ (self, x, y, width, height):
 super().__init__()
 self.width = width
 self.height = height
 self.x = x
 self.y = y
 self.image = pygame.Surface([self.width, self.height])
 self.image.fill(BLUE)
 self.rect = self.image.get_rect()
 self.rect.x = x
 self.rect.y = y
class Paddle(Wall):
 def __init__ (self,x, y, width, height):
 super().__init__(x, y, width, height)
 self.walls = None
 self.speed = 0
 self.my_score = None
 self.my_enemy = None
 def changespeed(self, change):
 self.speed+=change
 def changelength(self):
 self.height = self.my_score.lengthcal(self.my_enemy)
 self.image = pygame.Surface([self.width, self.height])
 self.image.fill(BLUE)
 self.rect = self.image.get_rect()
 self.rect.x = self.x
 self.rect.y = self.y
 def update(self):
 self.y += self.speed
 self.changelength()
 wall_hit_list = pygame.sprite.spritecollide(self, self.walls, False)
 for wall in wall_hit_list:
 if self.speed>0:
 self.y = wall.rect.top - self.height
 else:
 self.y = wall.rect.bottom
class Score():
 def __init__(self, x, y,color):
 self.score = 0
 self.color = color
 self.x = x
 self.y = y
 def plus(self):
 self.score += 1
 def lengthcal(self, enemy):
 if self.score <= enemy.my_score.score:
 return PADDLE_HEIGHT
 else:
 return PADDLE_HEIGHT-(self.score-enemy.my_score.score)*10
 def draw(self):
 font = pygame.font.SysFont(None,32)
 self.image = font.render(str(self.score), True, self.color, BLACK)
 self.rect = self.image.get_rect()
 self.rect.x = self.x
 self.rect.y = self.y
 screen.blit(self.image, self.rect)
pygame.init()
screen = pygame.display.set_mode([SCREEN_WIDTH, SCREEN_HEIGHT])
pygame.display.set_caption('Pong')
all_sprite_list = pygame.sprite.Group()
all_wall_list = pygame.sprite.Group()
wall_list = pygame.sprite.Group()
empty_list = pygame.sprite.Group()
wall = Wall(0, 0, SCREEN_WIDTH, 10)
wall_list.add(wall)
all_wall_list.add(wall)
all_sprite_list.add(wall)
wall.walls = empty_list
wall = Wall(0, SCREEN_HEIGHT-10, SCREEN_WIDTH, 10)
wall_list.add(wall)
all_wall_list.add(wall)
all_sprite_list.add(wall)
wall.walls = empty_list
score_left = Score(190, 30, WHITE)
score_right = Score(590, 30, WHITE)
paddle_left = Paddle(50, 350, 10, PADDLE_HEIGHT)
paddle_right = Paddle(SCREEN_WIDTH-50, 350, 10, PADDLE_HEIGHT)
all_wall_list.add(paddle_left)
all_sprite_list.add(paddle_left)
paddle_left.my_score = score_right
paddle_left.my_enemy = paddle_right
all_wall_list.add(paddle_right)
all_sprite_list.add(paddle_right)
paddle_right.my_score = score_left
paddle_right.my_enemy = paddle_left
ball = Ball(400,300,14,9)
all_sprite_list.add(ball)
paddle_left.walls = wall_list
paddle_right.walls = wall_list
ball.walls = all_wall_list
ball.deathcount_left = score_left
ball.deathcount_right = score_right
while not done:
 for event in pygame.event.get():
 if event.type == pygame.QUIT:
 done = True
 elif event.type == pygame.KEYDOWN:
 if event.key == pygame.K_UP:
 paddle_right.changespeed(-8)
 elif event.key == pygame.K_DOWN:
 paddle_right.changespeed(8)
 elif event.key == pygame.K_w:
 paddle_left.changespeed(-8)
 elif event.key == pygame.K_s:
 paddle_left.changespeed(8)
 elif event.type == pygame.KEYUP:
 if event.key == pygame.K_UP:
 paddle_right.changespeed(8)
 elif event.key == pygame.K_DOWN:
 paddle_right.changespeed(-8)
 elif event.key == pygame.K_w:
 paddle_left.changespeed(8)
 elif event.key == pygame.K_s:
 paddle_left.changespeed(-8)
 all_sprite_list.update()
 if paddle_left.height<30 or paddle_right.height<30:
 break
 screen.fill(BLACK)
 score_left.draw()
 score_right.draw()
 all_sprite_list.draw(screen)
 pygame.display.flip()
pygame.quit()

Answer 1

This is a short and very incomplete list of some small things that could be done differently:

• Be wary of initializing things to None; it can produce some annoying bugs later on where Python yells at you for using a Nonetype where it expects something else:

  # In Ball
  self.walls = pygame.sprite.Group()
  self.deathcount_left = Score(...)
  self.deathcount_right = Score(...)
  ...
  # In Paddle
  self.my_score = ball.deathcount_left
  self.enemy_score = ball.deathcount_right
  

Alternately, you could add to the constructor for Paddle to take in 2 Scores--yours and the enemy's.

• Do you intend for anything other than Paddle to inherit from Wall? If not, you don't need Wall at all because Wall.__init__ is only ever called in Paddle.__init__. Though not totally necessary, you could do away with Wall and copy over its constructor into Paddle's, though some might cringe at the length of the result.

I'm hesitant to add any more for fear of misleading you, but OOP aside, some small stylistic notes:

• It's generally considered good practice to leave some sort of comment describing your classes/functions/etc., if only so that as your work expands you don't have to read code to figure out what a function does.

Ball.update:

• You can move self.rect.y += self.speed_y just below self.rect.x += self.speed_x--it occurs regardless of the condition.

• Instead of using a nested if statement (if self.index == 1 etc.) you can rewrite with elif

  if self.index == 1:
   self.index = 0
  elif wall_hit_list:
   self.speed_x *= -1
  else:
   wall_hit_list = ...
   if wall_hit_list:
   self.speed_y *= -1
   self.index = 1