While teaching myself how to use pygame I discovered a distinct lack of the ability

to handle sprite sheets. After some digging on the internet I came across a class

that did everything I needed. I cleaned up the code a bit and added an additional

function to load a strip of images.

# This class handles sprite sheets
# This was taken from www.scriptefun.com/transcript-2-using
# sprite-sheets-and-drawing-the-background
# I've added some code to fail if the file wasn't found..
# Note: When calling images_at the rect is the format:
# (x, y, x + offset, y + offset)

import pygame

class spritesheet(object):
    def __init__(self, filename):
        try:
            self.sheet = pygame.image.load(filename).convert()
        except pygame.error, message:
            print 'Unable to load spritesheet image:', filename
            raise SystemExit, message
    # Load a specific image from a specific rectangle
    def image_at(self, rectangle, colorkey = None):
        "Loads image from x,y,x+offset,y+offset"
        rect = pygame.Rect(rectangle)
        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, pygame.RLEACCEL)
        return image
    # Load a whole bunch of images and return them as a list
    def images_at(self, rects, colorkey = None):
        "Loads multiple images, supply a list of coordinates" 
        return [self.image_at(rect, colorkey) for rect in rects]
    # Load a whole strip of images
    def load_strip(self, rect, image_count, colorkey = None):
        "Loads a strip of images and returns them as a list"
        tups = [(rect[0]+rect[2]*x, rect[1], rect[2], rect[3])
                for x in range(image_count)]
        return self.images_at(tups, colorkey)

Here is a quick example on how you would use this

import spritesheet
...
ss = spritesheet.spriteshee('somespritesheet.png')
# Sprite is 16x16 pixels at location 0,0 in the file...
image = ss.image_at((0, 0, 16, 16))
images = []
# Load two images into an array, their transparent bit is (255, 255, 255)
images = ss.images_at((0, 0, 16, 16),(17, 0, 16,16), colorkey=(255, 255, 255))
...

Here is a sprite strip animation iterator built on spritesheet.spritesheet

import spritesheet

class SpriteStripAnim(object):
    """sprite strip animator
    
    This class provides an iterator (iter() and next() methods), and a
    __add__() method for joining strips which comes in handy when a
    strip wraps to the next row.
    """
    def __init__(self, filename, rect, count, colorkey=None, loop=False, frames=1):
        """construct a SpriteStripAnim
        
        filename, rect, count, and colorkey are the same arguments used
        by spritesheet.load_strip.
        
        loop is a boolean that, when True, causes the next() method to
        loop. If False, the terminal case raises StopIteration.
        
        frames is the number of ticks to return the same image before
        the iterator advances to the next image.
        """
        self.filename = filename
        ss = spritesheet.spritesheet(filename)
        self.images = ss.load_strip(rect, count, colorkey)
        self.i = 0
        self.loop = loop
        self.frames = frames
        self.f = frames
    def iter(self):
        self.i = 0
        self.f = self.frames
        return self
    def next(self):
        if self.i >= len(self.images):
            if not self.loop:
                raise StopIteration
            else:
                self.i = 0
        image = self.images[self.i]
        self.f -= 1
        if self.f == 0:
            self.i += 1
            self.f = self.frames
        return image
    def __add__(self, ss):
        self.images.extend(ss.images)
        return self

And an example usage of sprite_strip_anim.SpriteStripAnim

"""
Sprite strip animator demo

Requires spritesheet.spritesheet and the Explode1.bmp through Explode5.bmp
found in the sprite pack at
http://lostgarden.com/2005/03/download-complete-set-of-sweet-8-bit.html

I had to make the following addition to method spritesheet.image_at in
order to provide the means to handle sprite strip cells with borders:

            elif type(colorkey) not in (pygame.Color,tuple,list):
                colorkey = image.get_at((colorkey,colorkey))
"""
import sys
import pygame
from pygame.locals import Color, KEYUP, K_ESCAPE, K_RETURN
import spritesheet
from sprite_strip_anim import SpriteStripAnim

surface = pygame.display.set_mode((100,100))
FPS = 120
frames = FPS / 12
strips = [
    SpriteStripAnim('Explode1.bmp', (0,0,24,24), 8, 1, True, frames),
    SpriteStripAnim('Explode2.bmp', (0,0,12,12), 7, 1, True, frames),
    SpriteStripAnim('Explode3.bmp', (0,0,48,48), 4, 1, True, frames) +
    SpriteStripAnim('Explode3.bmp', (0,48,48,48), 4, 1, True, frames),
    SpriteStripAnim('Explode4.bmp', (0,0,24,24), 6, 1, True, frames),
    SpriteStripAnim('Explode5.bmp', (0,0,48,48), 4, 1, True, frames) +
    SpriteStripAnim('Explode5.bmp', (0,48,48,48), 4, 1, True, frames),
]
black = Color('black')
clock = pygame.time.Clock()
n = 0
strips[n].iter()
image = strips[n].next()
while True:
    for e in pygame.event.get():
        if e.type == KEYUP:
            if e.key == K_ESCAPE:
                sys.exit()
            elif e.key == K_RETURN:
                n += 1
                if n >= len(strips):
                    n = 0
                strips[n].iter()
    surface.fill(black)
    surface.blit(image, (0,0))
    pygame.display.flip()
    image = strips[n].next()
    clock.tick(FPS)