Coding to Gaming
Tags: gamedev, beginners, python
Published: 2023-09-26 15:41:54

When people look at the python coding language they will typically refer to it as a backend specialized code and not expect to see an active interface regarding it. Well typically that is correct, however, but installing pygame may make those views change. Pygame is a set of modules that provides basic tools for beginner coders to learn how to program a game themselves. Within pygame it comes with various functions, sprites, sounds, and much more to assist with game development. Here I’ll give a short introduction to what pygame is capable of.
Ranging from adventure games, platforms, to simple clicking games pygame can cover a decent amount of ground based on the capabilities of the coder. However, despite being a quite welcome tool, if you look from high end (triple A companies) to indie developers (single to small group) it is quite unlikely you will find any games made with python. As I’ve said, pygame gives access to basic level tools, looking at that statement in another way, there’s nothing truly special about it. This setup does encourage programmers to learn the nuance of the game elements themselves which could help their development, rather than focusing on one highly specialized game engine that will unlikely provide meaningful experience. 
Take a look at the code below, it belongs to a simple pygame example called “Aliens”

```
import random, os.path

#import basic pygame modules
import pygame
from pygame.locals import *

#see if we can load more than standard BMP
if not pygame.image.get_extended():
    raise SystemExit("Sorry, extended image module required")


#game constants
MAX_SHOTS      = 2      #most player bullets onscreen
ALIEN_ODDS     = 22     #chances a new alien appears
BOMB_ODDS      = 60    #chances a new bomb will drop
ALIEN_RELOAD   = 12     #frames between new aliens
SCREENRECT     = Rect(0, 0, 640, 480)
SCORE          = 0

main_dir = os.path.split(os.path.abspath(__file__))[0]

def load_image(file):
    "loads an image, prepares it for play"
    file = os.path.join(main_dir, 'data', file)
    try:
        surface = pygame.image.load(file)
    except pygame.error:
        raise SystemExit('Could not load image "%s" %s'%(file, pygame.get_error()))
    return surface.convert()

def load_images(*files):
    imgs = []
    for file in files:
        imgs.append(load_image(file))
    return imgs


class dummysound:
    def play(self): pass

def load_sound(file):
    if not pygame.mixer: return dummysound()
    file = os.path.join(main_dir, 'data', file)
    try:
        sound = pygame.mixer.Sound(file)
        return sound
    except pygame.error:
        print ('Warning, unable to load, %s' % file)
    return dummysound()



# each type of game object gets an init and an
# update function. the update function is called
# once per frame, and it is when each object should
# change it's current position and state. the Player
# object actually gets a "move" function instead of
# update, since it is passed extra information about
# the keyboard


class Player(pygame.sprite.Sprite):
    speed = 10
    bounce = 24
    gun_offset = -11
    images = []
    def __init__(self):
        pygame.sprite.Sprite.__init__(self, self.containers)
        self.image = self.images[0]
        self.rect = self.image.get_rect(midbottom=SCREENRECT.midbottom)
        self.reloading = 0
        self.origtop = self.rect.top
        self.facing = -1

    def move(self, direction):
        if direction: self.facing = direction
        self.rect.move_ip(direction*self.speed, 0)
        self.rect = self.rect.clamp(SCREENRECT)
        if direction < 0:
            self.image = self.images[0]
        elif direction > 0:
            self.image = self.images[1]
        self.rect.top = self.origtop - (self.rect.left//self.bounce%2)

    def gunpos(self):
        pos = self.facing*self.gun_offset + self.rect.centerx
        return pos, self.rect.top


class Alien(pygame.sprite.Sprite):
    speed = 13
    animcycle = 12
    images = []
    def __init__(self):
        pygame.sprite.Sprite.__init__(self, self.containers)
        self.image = self.images[0]
        self.rect = self.image.get_rect()
        self.facing = random.choice((-1,1)) * Alien.speed
        self.frame = 0
        if self.facing < 0:
            self.rect.right = SCREENRECT.right

    def update(self):
        self.rect.move_ip(self.facing, 0)
        if not SCREENRECT.contains(self.rect):
            self.facing = -self.facing;
            self.rect.top = self.rect.bottom + 1
            self.rect = self.rect.clamp(SCREENRECT)
        self.frame = self.frame + 1
        self.image = self.images[self.frame//self.animcycle%3]


class Explosion(pygame.sprite.Sprite):
    defaultlife = 12
    animcycle = 3
    images = []
    def __init__(self, actor):
        pygame.sprite.Sprite.__init__(self, self.containers)
        self.image = self.images[0]
        self.rect = self.image.get_rect(center=actor.rect.center)
        self.life = self.defaultlife

    def update(self):
        self.life = self.life - 1
        self.image = self.images[self.life//self.animcycle%2]
        if self.life <= 0: self.kill()


class Shot(pygame.sprite.Sprite):
    speed = -11
    images = []
    def __init__(self, pos):
        pygame.sprite.Sprite.__init__(self, self.containers)
        self.image = self.images[0]
        self.rect = self.image.get_rect(midbottom=pos)

    def update(self):
        self.rect.move_ip(0, self.speed)
        if self.rect.top <= 0:
            self.kill()


class Bomb(pygame.sprite.Sprite):
    speed = 9
    images = []
    def __init__(self, alien):
        pygame.sprite.Sprite.__init__(self, self.containers)
        self.image = self.images[0]
        self.rect = self.image.get_rect(midbottom=
                    alien.rect.move(0,5).midbottom)

    def update(self):
        self.rect.move_ip(0, self.speed)
        if self.rect.bottom >= 470:
            Explosion(self)
            self.kill()


class Score(pygame.sprite.Sprite):
    def __init__(self):
        pygame.sprite.Sprite.__init__(self)
        self.font = pygame.font.Font(None, 20)
        self.font.set_italic(1)
        self.color = Color('white')
        self.lastscore = -1
        self.update()
        self.rect = self.image.get_rect().move(10, 450)

    def update(self):
        if SCORE != self.lastscore:
            self.lastscore = SCORE
            msg = "Score: %d" % SCORE
            self.image = self.font.render(msg, 0, self.color)



def main(winstyle = 0):
    # Initialize pygame
    pygame.init()
    if pygame.mixer and not pygame.mixer.get_init():
        print ('Warning, no sound')
        pygame.mixer = None

    # Set the display mode
    winstyle = 0  # |FULLSCREEN
    bestdepth = pygame.display.mode_ok(SCREENRECT.size, winstyle, 32)
    screen = pygame.display.set_mode(SCREENRECT.size, winstyle, bestdepth)

    #Load images, assign to sprite classes
    #(do this before the classes are used, after screen setup)
    img = load_image('player1.gif')
    Player.images = [img, pygame.transform.flip(img, 1, 0)]
    img = load_image('explosion1.gif')
    Explosion.images = [img, pygame.transform.flip(img, 1, 1)]
    Alien.images = load_images('alien1.gif', 'alien2.gif', 'alien3.gif')
    Bomb.images = [load_image('bomb.gif')]
    Shot.images = [load_image('shot.gif')]

    #decorate the game window
    icon = pygame.transform.scale(Alien.images[0], (32, 32))
    pygame.display.set_icon(icon)
    pygame.display.set_caption('Pygame Aliens')
    pygame.mouse.set_visible(0)

    #create the background, tile the bgd image
    bgdtile = load_image('background.gif')
    background = pygame.Surface(SCREENRECT.size)
    for x in range(0, SCREENRECT.width, bgdtile.get_width()):
        background.blit(bgdtile, (x, 0))
    screen.blit(background, (0,0))
    pygame.display.flip()

    #load the sound effects
    boom_sound = load_sound('boom.wav')
    shoot_sound = load_sound('car_door.wav')
    if pygame.mixer:
        music = os.path.join(main_dir, 'data', 'house_lo.wav')
        pygame.mixer.music.load(music)
        pygame.mixer.music.play(-1)

    # Initialize Game Groups
    aliens = pygame.sprite.Group()
    shots = pygame.sprite.Group()
    bombs = pygame.sprite.Group()
    all = pygame.sprite.RenderUpdates()
    lastalien = pygame.sprite.GroupSingle()

    #assign default groups to each sprite class
    Player.containers = all
    Alien.containers = aliens, all, lastalien
    Shot.containers = shots, all
    Bomb.containers = bombs, all
    Explosion.containers = all
    Score.containers = all

    #Create Some Starting Values
    global score
    alienreload = ALIEN_RELOAD
    kills = 0
    clock = pygame.time.Clock()

    #initialize our starting sprites
    global SCORE
    player = Player()
    Alien() #note, this 'lives' because it goes into a sprite group
    if pygame.font:
        all.add(Score())


    while player.alive():

        #get input
        for event in pygame.event.get():
            if event.type == QUIT or \
                (event.type == KEYDOWN and event.key == K_ESCAPE):
                    return
        keystate = pygame.key.get_pressed()

        # clear/erase the last drawn sprites
        all.clear(screen, background)

        #update all the sprites
        all.update()

        #handle player input
        direction = keystate[K_RIGHT] - keystate[K_LEFT]
        player.move(direction)
        firing = keystate[K_SPACE]
        if not player.reloading and firing and len(shots) < MAX_SHOTS:
            Shot(player.gunpos())
            shoot_sound.play()
        player.reloading = firing

        # Create new alien
        if alienreload:
            alienreload = alienreload - 1
        elif not int(random.random() * ALIEN_ODDS):
            Alien()
            alienreload = ALIEN_RELOAD

        # Drop bombs
        if lastalien and not int(random.random() * BOMB_ODDS):
            Bomb(lastalien.sprite)

        # Detect collisions
        for alien in pygame.sprite.spritecollide(player, aliens, 1):
            boom_sound.play()
            Explosion(alien)
            Explosion(player)
            SCORE = SCORE + 1
            player.kill()

        for alien in pygame.sprite.groupcollide(shots, aliens, 1, 1).keys():
            boom_sound.play()
            Explosion(alien)
            SCORE = SCORE + 1

        for bomb in pygame.sprite.spritecollide(player, bombs, 1):
            boom_sound.play()
            Explosion(player)
            Explosion(bomb)
            player.kill()

        #draw the scene
        dirty = all.draw(screen)
        pygame.display.update(dirty)

        #cap the framerate
        clock.tick(40)

    if pygame.mixer:
        pygame.mixer.music.fadeout(1000)
    pygame.time.wait(1000)
    pygame.quit()



#call the "main" function if running this script
if __name__ == '__main__': main()
```


![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/c84manrp74vq7l2ednpu.png)



When you run the code a new window appears containing the game “Aliens”. This game has simple controls along with a simple objective. The user controls the military vehicle with the left and right arrow keys for movement and the spacebar to shoot a missile to attack the UFOs gaining points. Going under the hood we see the above code declaring the aspects of the game from the player vehicle, UFOs, missiles, explosions, and so on. 
```
class Player(pygame.sprite.Sprite):
    speed = 10
    bounce = 24
    gun_offset = -11
    images = []
    def __init__(self):
        pygame.sprite.Sprite.__init__(self, self.containers)
        self.image = self.images[0]
        self.rect = self.image.get_rect(midbottom=SCREENRECT.midbottom)
        self.reloading = 0
        self.origtop = self.rect.top
        self.facing = -1

    def move(self, direction):
        if direction: self.facing = direction
        self.rect.move_ip(direction*self.speed, 0)
        self.rect = self.rect.clamp(SCREENRECT)
        if direction < 0:
            self.image = self.images[0]
        elif direction > 0:
            self.image = self.images[1]
        self.rect.top = self.origtop - (self.rect.left//self.bounce%2)

    def gunpos(self):
        pos = self.facing*self.gun_offset + self.rect.centerx
        return pos, self.rect.top
```
This class sets the attributes of the player and uses those values later to interact with the program as a whole. There are also classes that cover the Bomb, Shot, Explosion, and of course the Alien. And in some of these classes they share similar attributes such as speed, in this context speed will decide how quickly objects can move within the game. . 

```
class Alien(pygame.sprite.Sprite):
    speed = 13
    animcycle = 12
    images = []
    def __init__(self):
        pygame.sprite.Sprite.__init__(self, self.containers)
        self.image = self.images[0]
        self.rect = self.image.get_rect()
        self.facing = random.choice((-1,1)) * Alien.speed
        self.frame = 0
        if self.facing < 0:
            self.rect.right = SCREENRECT.right

    def update(self):
        self.rect.move_ip(self.facing, 0)
        if not SCREENRECT.contains(self.rect):
            self.facing = -self.facing;
            self.rect.top = self.rect.bottom + 1
            self.rect = self.rect.clamp(SCREENRECT)
        self.frame = self.frame + 1
        self.image = self.images[self.frame//self.animcycle%3]
```

Here is the Alien class that sets the attributes for the endlessly spawning enemies in the game. Now let’s look at this line  `self.rect = self.image.get_rect()` here a method to give Alien a rectangle, now what does it mean to give a rectangle to a flying disc dropping bombs? It’s to allow easier ways for the game aspects to interact with each other. We can manipulate the collisions between the missiles and the player utilizing rectangles to help adjust hitboxes and sprite movement. 

```
 # Detect collisions
        for alien in pygame.sprite.spritecollide(player, aliens, 1):
            boom_sound.play()
            Explosion(alien)
            Explosion(player)
            SCORE = SCORE + 1
            player.kill()

        for alien in pygame.sprite.groupcollide(shots, aliens, 1, 1).keys():
            boom_sound.play()
            Explosion(alien)
            SCORE = SCORE + 1

        for bomb in pygame.sprite.spritecollide(player, bombs, 1):
            boom_sound.play()
            Explosion(player)
            Explosion(bomb)
            player.kill()
```

In these lines of code they cover different scenarios of collisions within the game. From top to bottom, what happens if a UFO and the player collide, what happens if a missile and a UFO collide, and what happens if a bomb and the player collide. These outcomes decide if the score rises or the game ends with the player’s death.


 After various information is laid out for us you may notice that the actual gameplay of this code is all written within a while loop. The loop essentially runs making aliens endlessly spawning at set increments and reads the player input keys to control the vehicle. And if we look at the condition for the while loop `while player.alive()` The loop will end when the player is “dead” and the conditions to cause this are essentially when the player collides with a bomb or a UFO. When the player status changes the loop essentially ends and the last two lines of the "main" function code run.
```
 pygame.time.wait(1000)
 pygame.quit()
```
The program will wait one second and the game will quit, closing the window and ending the code.
Hopefully this brief introduction to pygame can provide some insight to future game developers that want to experiment around within python.





Sources:

- Github of '[Aliens](https://github.com/xamox/pygame/blob/master/examples/aliens.py)'

- Installing [Pygame](https://www.pygame.org/wiki/GettingStarted)

- To simply play 'Aliens' after installing pygame you can enter `python3 -m pygame.examples.aliens` into your terminal and it'll launch the game.

- About [Pygame](https://www.pygame.org/wiki/about?parent=)