import gif

file = open ('checkerboard.gif', 'rb')
reader = gif.Reader ()
reader.feed (file.read ())
if reader.has_screen_descriptor ():
    print ('Size: %dx%d' % (reader.width, reader.height))
    print ('Colors: %s' % repr (reader.color_table))
    for block in reader.blocks:
        if isinstance (block, gif.Image):
            print ('Pixels: %s' % repr (block.get_pixels ()))
    if reader.has_unknown_block ():
        print ('Encountered unknown block')
    elif not reader.is_complete ():
        print ('Missing trailer')
else:
    print ('Not a valid GIF file')
