Sprites

Sprites are probably one of the most important parts of using Pygame. They aren't strictly necessary, but they can make your code simpler (cool) and faster (awesome!).

Thepygame.sprite.Spriteclass is a base class which gives basic functionality for game objects. Some functionality it provides by default:

• Batch rectangular and circular collision detection
• Batch updates
• Batch drawing

Some general steps for using Sprites:

1. Extend thepygame.sprite.Spriteclass
2. Call the superclass's init method
3. Create the updatemethod
4. Assign therect,image, and optionally theradiusattributes
   • rectis used for drawing (position / size) and rectangular collision detection
   • imageis used for drawing: it's a Surface
   • radiusis used for circular collision detection
5. Add instances of your subclass into Groups

So what is a Group? A Group (pygame.sprite.Group) is an object which represents a collection of Sprites. You can use groups to update each sprite in the group at the same time, or to draw each sprite in the group at the same time.

Perhaps the coolest built-in functionality of Groups, however, is thepygame.sprite.groupcollidefunction. This allows you to specify two groups, and determine if any sprite from the first group is colliding with any sprite in the second group. We can specify lots of things for this:

• The two groups we want to check (group1andgroup2)
• dokill1anddokill2: if one of these is True, any colliding Sprites in the respective group are removed automatically. This means no more confusing list modifications!
• collided: this is a function which takes two Sprites and tells if they're colliding - this means we can specify how to detect collisions between groups. Usepygame.sprite.collide_rect,pygame.sprite.collide_circle, or a custom collision function!

collidegroupreturns aSprite_Dictobject - this is a dictionary which maps Sprites fromgroup1to all the Sprites ingroup2that it was colliding with. This allows us to do any necessary cleanup code for the removed objects.

Here's a quick Sprite example using Dots:

class Dot(pygame.sprite.Sprite):
    def __init__(self, x, y):
        super(Dot, self).__init__()
        self.radius = random.randint(5, 20)
        self.x, self.y = x, y
        self.xSpeed = random.randint(-10, 10)
        self.ySpeed = random.randint(-10, 10)
        self.rect = pygame.Rect(x - self.radius, y - self.radius,
                                2 * self.radius, 2 * self.radius)
        self.image = pygame.Surface((2 * self.radius, 2 * self.radius),
                                    pygame.SRCALPHA)  # make it transparent
        self.image = self.image.convert_alpha()
        r = random.randint(0, 255)
        g = random.randint(0, 255)
        b = random.randint(0, 255)
        pygame.draw.circle(self.image, (r, g, b),
                           (self.radius, self.radius), self.radius)

    def getRect(self):  # GET REKT
        self.rect = pygame.Rect(self.x - self.radius, self.y - self.radius,
                                2 * self.radius, 2 * self.radius)

    def update(self, screenWidth, screenHeight):
        self.x += self.xSpeed
        self.y += self.ySpeed
        if self.x < 0:
            self.x = screenWidth
        elif self.x > screenWidth:
            self. x = 0
        if self.y < 0:
            self.y = screenHeight
        elif self.y > screenHeight:
            self.y = 0
        self.getRect()

pygame.init()
screen = pygame.display.set_mode((500, 500))
clock = pygame.time.Clock()

dots = pygame.sprite.Group()
playing = True
while playing:
    clock.tick(50)
    for event in pygame.event.get():
        if event.type == pygame.MOUSEBUTTONDOWN:
            d = Dot(*event.pos)
            dots.add(d)
        elif event.type == pygame.QUIT:
            playing = False
    dots.update(500, 500)
    screen.fill((255, 255, 255))
    dots.draw(screen)
    pygame.display.flip()
pygame.quit()

Check out the Sprites reference here.