Python in Game Development

Denis Kovalev

Software Developer at DataArt

About me

• 6+ years in IT

• started as C developer

• 3+ years Python

• Linux, bash, Perl, Java

• DataArt (http://www.dataart.com)

• http://about.me/denis.kovalev

Why Python?

• Python

• maintenance

• libraries

• learn

Existing “Python” games

• Battlefield 2 & Battlefield 2142

• Eve Online

• Mount & Blade

• Civilization IV

• Severance: Blade of Darkness

• Greyhawk: Temple of Elemental Evil

GUI

• Tkinter, PyGTK, PyQt

• PyGame

• Kivy

• Pyggel (Python Graphical Game Engine + Libraries)

• Panda3D

• Pyglet + Cocos2d

2D

3D

Pygame

+ SDL (Simple Directmedia Layer) library

+ Stable and well-documented

+ Examples and tutorials

- Not pythonic

+ Easy & powerful

Pygame Drawing Concept

Create window

1. import pygame
3. pygame.init()
4. screen = pygame.display.set_mode((640, 480))
6. while 1:
7. for event in pygame.event.get():
8. if event.type == pygame.QUIT:
9. raise SystemExit("QUIT")

​

Pygame “Hello, World!”

1. import pygame
2. ​
3. pygame.init()
4. WHITE = pygame.Color(255, 255, 255)
5. width, height = (640, 480)
6. screen = pygame.display.set_mode((width, height))
8. font = pygame.font.Font(None, 50)
9. text = font.render("Hello, World!", True, WHITE)
11. # Draw text on screen
12. screen.blit(text, text.get_rect(centerx=width/2., centery=height/2.))
13. pygame.display.update()
15. while 1:
16. for event in pygame.event.get():
17. if event.type == pygame.QUIT:
18. raise SystemExit("QUIT")

Pygame key press

1. def get_text(msg="Hello, World!"):
2. font = pygame.font.Font(None, 50)
3. text = font.render(msg, True, WHITE)
4. return text
5. delta_x, delta_y = (0, 0)
6. step = 20
7. while 1:
8. screen.fill(BLACK)
9. for event in pygame.event.get():
10. if event.type == pygame.QUIT:
11. raise SystemExit("QUIT")
12. elif event.type == pygame.KEYDOWN and event.key == pygame.K_DOWN:
13. delta_y += step
14. elif event.type == pygame.KEYDOWN and event.key == pygame.K_UP:
15. delta_y -= step
16. …
17. elif event.type == pygame.KEYDOWN and event.key == pygame.K_r:
18. delta_x, delta_y = (0, 0)
19. text = get_text()
20. screen.blit(text, text.get_rect(centerx=width/2. + delta_x, centery=height/2. + delta_y))
21. pygame.display.update()

​

Pygame surfaces

1. yellow_surface = pygame.Surface((width, height))
2. yellow_surface.fill(YELLOW)
3. green_surface = pygame.Surface((width/2, height/2))
4. green_surface.fill(GREEN)
6. def draw_circle(pos, radius=width/8):
7. pygame.draw.circle(yellow_surface, GREEN, pos, radius)
8. pygame.draw.circle(green_surface, YELLOW, pos, radius)
9. ​
10. while 1:
11. for event in pygame.event.get():
12. if event.type == pygame.MOUSEBUTTONDOWN and event.button == 1:
13. move = True
14. elif event.type == pygame.MOUSEBUTTONUP and event.button == 1:
15. move = False
16. if move:
17. yellow_surface.fill(YELLOW)
18. green_surface.fill(GREEN)
19. pos = pygame.mouse.get_pos()
20. draw_circle(pos)
21. screen.blit(yellow_surface, (0, 0))
22. screen.blit(green_surface, (0, 0))
23. pygame.display.update()

Pygame objects collision

1. static_rect = pygame.Rect((width/3, height/3), (width/3, height/3))
2. moving_rect = pygame.Rect((width*2/3, height*2/3), (width/6, height/6))
4. def draw_rects(pos):
5. moving_rect.centerx, moving_rect.centery = pos
6. pygame.draw.rect(yellow_surface, GREEN, moving_rect)
7. if moving_rect.colliderect(static_rect):
8. pygame.draw.rect(yellow_surface, PURPLE, static_rect)
9. else:
10. pygame.draw.rect(yellow_surface, BLUE, static_rect)
12. pos = (0, 0)
13. move = False
14. while 1:
15. for event in pygame.event.get():
16. ...
17. if move:
18. yellow_surface.fill(YELLOW)
19. pos = pygame.mouse.get_pos()
20. draw_rects(pos)
21. screen.blit(yellow_surface, (0, 0))
22. pygame.display.update()

Pygame Sprites - create

1. class Ball(pygame.sprite.Sprite):
2. radius = 25
3. groups = []
4. acceleration = 1
5. def __init__(self, pos):
6. pygame.sprite.Sprite.__init__(self, self.groups)
7. self.image = pygame.Surface((Ball.radius * 2, Ball.radius * 2))
8. self.image.fill(YELLOW)
9. self.image.convert_alpha()
10. self.rect = self.image.get_rect()
11. self.radius = Ball.radius
12. self.velocity = 0
13. pygame.draw.circle(self.image, BLUE, self.rect.center, self.radius, 0)
14. self.rect.center = pos

Pygame Sprites - move

1. class Ball(pygame.sprite.Sprite):
2. ….
3. def update(self):
4. if self.rect.top < height: # inside the screen?
5. self.rect.move_ip(0, self.velocity)
6. bricks = pygame.sprite.spritecollide(self, static, False)
7. if bricks:
8. brick = bricks[0]
9. self.rect.bottom = brick.rect.top # place the ball on top of the brick
10. self.velocity *= -0.9 # bounce with speed loss
11. if 0 > self.velocity > -0.1: # prevent infinite bounce
12. self.velocity = 0
13. else:
14. self.velocity += Ball.acceleration

​

Pygame Sprites

1. allsprites = pygame.sprite.Group()
2. Ball.groups = allsprites
4. static = pygame.sprite.Group()
5. Brick.groups = allsprites, static
7. timer = pygame.time.Clock()
8. screen.blit(yellow_surface, (0, 0))
9. while 1:
10. timer.tick(60)
11. for event in pygame.event.get():
12. if event.type == pygame.QUIT:
13. raise SystemExit("QUIT")
14. elif event.type == pygame.MOUSEBUTTONDOWN and event.button == 1:
15. Ball(event.pos)
16. elif event.type == pygame.MOUSEBUTTONDOWN and event.button == 3:
17. Brick(event.pos)
18. elif event.type == pygame.KEYDOWN and event.key == pygame.K_r:
19. allsprites.empty()
20. static.empty()
21. allsprites.clear(screen, yellow_surface)
22. allsprites.update()
23. allsprites.draw(screen)
24. pygame.display.update()

​

Python Physics Engines

PyODE (Python bindings for The Open Dynamics Engine)

pyBox2D

Panda3D

Pymunk Physics Engine

• Based on Chipmunk2D

• Force & impulse

• Collisions

• Constraints

• Pygame & Pyglet modules

Pymunk basics

1. import pymunk as pm
3. space = pm.Space()
4. space.gravity = (0, -900.0)
6. class Ball(pm.Body):
7. def __init__(self, pos, mass=10, radius=25):
8. inertia = pm.moment_for_circle(mass, 0, radius, (0,0))
9. pm.Body.__init__(self, mass, inertia)
10. self.position = pos
11. self.radius = radius
12. def get_shape(self, elasticity=0.9):
13. shape = pm.Circle(self, self.radius, (0,0))
14. shape.elasticity = elasticity
15. return shape

Pygame + Pymunk

1. while 1:
2. for event in pygame.event.get():
3. if event.type == pygame.MOUSEBUTTONDOWN and event.button == 1:
4. body = Ball(to_pygame(event.pos))
5. shape = body.get_shape()
6. space.add(body, shape)
7. balls.append(shape)
8. elif event.type == pygame.MOUSEBUTTONDOWN and event.button == 3:
9. brick = Brick(to_pygame(event.pos))
10. space.add(brick)
11. bricks.append(brick)
13. ### Draw stuff here
14. ​
15. ### Update physics
16. fps = 60.0
17. space.step(1./fps)
19. pygame.display.flip()
20. clock.tick(fps)

Pyglet

Cocos2d

+ No dependencies

+ Pythonic

+ Images, audio, video in any format

- Not for games

+ Pyglet-based

+ For games, apps, GUI interaction

- Poor API docs

- Google does not help

+ OpenGL interface

+ Layers and scenes

Pygame vs Pyglet

1. import pygame
3. pygame.init()
4. screen = pygame.display.set_mode((640,480))
6. while 1:
7. for event in pygame.event.get():
8. if event.type == pygame.QUIT:
9. raise SystemExit("QUIT")

1. import pyglet
2. ​
3. screen = pyglet.window.Window(640,480)
4. ​
5. pyglet.app.run()

​

Pygame vs Pyglet

1. import pygame
3. pygame.init()
4. screen = pygame.display.set_mode((640,480))
6. while 1:
7. timer.tick(60)
8. for event in pygame.event.get():
9. if event.type == pygame.KEYDOWN and event.key == pygame.K_a:
10. print 'You pressed A'
11. #update objects here
12. pygame.display.update()

​

1. import pyglet
2. from pyglet.window import key
4. screen = pyglet.window.Window(640,480)
6. @screen.event
7. def on_key_press(symbol, modifiers):
8. if symbol == key.A:
9. print 'You pressed A'
11. def update(dt):
12. #update objects here
14. pyglet.clock.schedule_interval(update, 1/60.0)
15. pyglet.app.run()

​

Showtime!

Prerequisites

Python 2.6, 2.7, 3.3+

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pip install --upgrade http://pyglet.googlecode.com/archive/tip.zip

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pip install cocos2d

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Download images from http://bit.ly/pycon_game

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Map editors

Tiled - http://www.mapeditor.org

+ PyTMX

FIFE - http://www.fifengine.net

FIFE + Python = https://github.com/fifengine/python-tutorials

“Unknown Horizons”

“Zero-Projekt”

Examples and games

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pyvolley (cocos2d, pymunk) -

https://github.com/aikikode/pyvolley

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Minecraft in Python (pyglet, OpenGL) -

https://github.com/boskee/Minecraft

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“Nautili” (PyGame, Tiled)

https://github.com/aikikode/nautili

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pyhammerfight (cocos2d, pymunk) -

https://github.com/aikikode/pyhammerfight

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Presentation examples - https://bitbucket.org/aikikode/pygame_examples

Thanks to

• Cody Lovett for Pygame examples

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• QR Code Generator - http://goqr.me/

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• Syntax Highlighter - http://highlight.hohli.com/

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Thanks for your attention!

• skype: aikikode

• email: aikikode@gmail.com

• http://about.me/denis.kovalev

Questions?