file name format: 0001.png

 name = "{:04d}".format(1)

 0001

 str(name) + ".png"

#python lists
keeper_animation_north = []  
keeper_animation_south = []  
keeper_animation_east = []
keeper_animation_west = []

#LOAD 20 IMAGES FROM EACH FOLDER. FILE NAME FORMAT 0001.png
for i in range(1,21):
    name = "{:04d}".format(i) #BLENDER NAME FIX
    path = "assets/keeper/north/"+ str(name) +".png"
    keeper_animation_north.append(pygame.image.load(path).convert_alpha())
    path = "assets/keeper/south/" + str(name) +".png"
    keeper_animation_south.append(pygame.image.load(path).convert_alpha())
    path = "assets/keeper/east/" + str(name) +".png"
    keeper_animation_east.append(pygame.image.load(path).convert_alpha())
    path = "assets/keeper/west/" + str(name) +".png"
    keeper_animation_west.append(pygame.image.load(path).convert_alpha())

ANIMATION

self.image_list = keeper_animation_south
self.image = self.image_list[self.image_index]      

CHANGE ANIMATION

self.image_list = keeper_animation_north