[pygame] Creating several instances of same image

["Nick Lunt" <nick@javacat.f2s.com>]

Hi Folks,

Im attempting to write a little space invaders type game.

Im having problems working out how to get my aliens displayed onto the
screen and then being able to manipulate them.

I want the game to look like the original space invaders.

Here's the relevant code:

>class Alien(pygame.sprite.Sprite):
>    """ aliens only move as far left/right and the most left/right alien
can move """
>    def __init__(self):
>        pygame.sprite.Sprite.__init__(self)
>        self.image, self.rect = loadImg('alien.png')

># Now create some Aliens()
>   alienDict = {}
>    for alien in range(1,13):
>        alienDict[alien] = Alien()

Im thinking that Im doing this in completely the wrong way.

Could anyone point me in the right direction to get 12 aliens on the screen
(4 x 3).

Ive looked at the code from the Aliens demo included with pygame, but thats
different from what I want to do.

Also, I appreciate that my problem is probably as much python related as
pygame related, but Ive been doing python for about 4 months and want to
apply what I've learnt to pygame.

Ive attached the whole code in case that helps.

Many thanks
Nick.
import pygame
from pygame.locals import *
import sys

# image sizes:
#   defender.png 40 x 40
#   alien.png 30 x 20
#   laser.png 6 x 20

screenSize = (640,480)
black = (0,0,0)

def loadImg(img):
    image = pygame.image.load(img).convert()
    return image, image.get_rect()

class Defender(pygame.sprite.Sprite):
    def __init__(self):
        pygame.sprite.Sprite.__init__(self)
        self.image, self.rect = loadImg('defender.png')
        self.rect.move_ip(0,440)

    def moves(self, keyPressed):
        xvalue = 5
        if keyPressed == 'K_RIGHT' and self.rect.right < 640:
            self.rect.move_ip(xvalue,0)
        elif keyPressed == 'K_LEFT' and self.rect.left > 0:
            self.rect.move_ip(-xvalue,0)
        else:
            pass

class Alien(pygame.sprite.Sprite):
    """ aliens only move as far left/right and the most left/right alien can move """
    def __init__(self):
        pygame.sprite.Sprite.__init__(self)
        self.image, self.rect = loadImg('alien.png')

class Laser(pygame.sprite.Sprite):
    def __init__(self):
        pygame.sprite.Sprite.__init__(self)
        self.image, self.rect = loadImg('laser.png')

def main():
    screen = pygame.display.set_mode(screenSize)
    pygame.display.set_caption('Invaders')
    background = pygame.Surface(screen.get_size()).convert()
    background.fill(black)
    screen.blit(background, (0,0))
    pygame.key.set_repeat(15,15)

    defender = Defender()
    laser = Laser()

    # Aliens
    alienDict = {}
    for alien in range(1,13):
        alienDict[alien] = Alien()
        print alienDict[alien].image
    print alienDict
        
    allsprites = pygame.sprite.RenderPlain((defender)) # + laser/aliens

    while True:
        for event in pygame.event.get():
            if event.type == pygame.QUIT:
                sys.exit()
            if event.type == KEYDOWN:
                if event.key == K_RIGHT:
                    defender.moves('K_RIGHT')
                if event.key == K_LEFT:
                    defender.moves('K_LEFT')

        screen.blit(background, (0,0))
        allsprites.draw(screen)
        pygame.display.flip()

if __name__ == '__main__':
    main()