[pygame] spritesheets and animation

[Devon Scott-Tunkin <djvonfunkin@xxxxxxxxx>]

Hi I've just started using pygame and python in general as of a week ago and I'm probably trying to get up the mountain too soon. In the following program I've frankensteined in order to simply repeat a 4 frame walk cycle animation, I can't get the sprite to display, all I see is black.  If anyone can point me to what I'm doing wrong I'd appreciate it.  

Thanks,

Devon

import os, pygame
from pygame.locals import *

SCREENRECT = Rect(0, 0, 320, 240)

class Spritesheet:
    def __init__(self, filename):
        self.sheet = pygame.image.load(os.path.join('data', filename)).convert()
    def imgat(self, rect, colorkey = None):
        rect = Rect(rect)
        image = pygame.Surface(rect.size).convert()
        image.blit(self.sheet, (0, 0),
 rect)
        if colorkey is not None:
            if colorkey is -1:
                colorkey = image.get_at((0, 0))
            image.set_colorkey(colorkey, RLEACCEL)
        return image
    #def imgsat(self, rects, colorkey = None):
    #    imgs = []
    #    for rect in rects:
    #        imgs.append(self.imgat(rect, colorkey))
    #    return imgs

def geneimages():
    spritesheet = Spritesheet('sprite_gene.png')
    return [spritesheet.imgat((0, 0, 16, 32), -1),  
 
            spritesheet.imgat((17, 0, 16, 32), -1),  
            spritesheet.imgat((33, 0, 16, 32), -1),   
            spritesheet.imgat((49, 0, 16, 32), -1)]
    
class Gene(pygame.sprite.Sprite):
    def __init__(self, fps = 10):
        pygame.sprite.Sprite.__init__(self)
        # Track the time we started, and the time between updates.
        # Then we can figure out when we have to switch the image.
        self._frame = 0
        self.image = self._images[self._frame]
        self.rect =
 self.image.get_rect()
        self._start = pygame.time.get_ticks()
        self._delay = 1000 / fps
        self._last_update = 0

 # Call update to set our first image.
        self.update(pygame.time.get_ticks())
        
    def update(self, t):
        # Note that this doesn't work if it's been more that self._delay
        # time between calls to update(); we only update the image once
        # then, but it really should be updated twice.

        if t - self._last_update > self._delay:
            self._frame +=
 1
            if self._frame >= len(self._images): self._frame = 0
            self.image = self._images[self._frame]
            self._last_update = t

def main():
    pygame.init()
    screen = pygame.display.set_mode(SCREENRECT.size)
    Gene._images = geneimages()
    gene = Gene()                            
    
 
    genesprite = pygame.sprite.RenderUpdates()

    # Set-up background surface
    global background
    background = "">   
 background = "">
    # keep track of time
    clock = pygame.time.Clock()

    # Blit everything to the screen
    screen.blit(background, (0, 0))
    pygame.display.flip()
    
    # game loop
    while 1:
        # maintain frame rate
        clock.tick(30)
        
        # get input
        for event in pygame.event.get():
            if event.type == QUIT   \
               or (event.type == KEYDOWN and   
 \
                   event.key == K_ESCAPE):
                return

        # clear sprites
        genesprite.clear(screen, background)

        # update sprites
        genesprite.update(4)

        # redraw sprites
        genesprite.draw(screen)
        pygame.display.flip()

        

if __name__ == '__main__': main()

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