Text-based terrain generator (Part 2)

I've updated my text-based terrain generator a lot. Even though I haven't worked on it all that much. I really just want to know, like usual, is there anything I can improve? How can I shorten the code? What can be made more efficient? Yada yada yada...

#!/usr/bin/env pythonfrom random import choicefrom os import system, nameclass Tiles(object):    tree = '\033[7;1;32m  \033[0m'    land = '\033[7;32m  \033[0m'    sand = '\033[7;1;33m  \033[0m'    water = '\033[7;1;34m  \033[0m'class Sizes(object):    small = 10    med1 = 20    med2 = 30    large = 40sizes = (    Sizes.small, Sizes.med1, Sizes.med2, Sizes.large)tiles = (    Tiles.land, Tiles.sand, Tiles.tree, Tiles.water)def generate(world_size):    system('cls' if name == 'nt' else 'clear')       for _ in range(world_size):            print(''.join(choice(tiles) for _ in range(world_size)))if __name__ == "__main__":    generate(choice(sizes))

Also, this is python 2.7 I just prefer to use print() over print.