def direction(self, other):
offset = (other.x - self.x, other.y - self.y)
for d in direction_by_abr.values():
if d.offset == offset:
return d
raise ValueError(other)
def adjacent_tiles(self, tile):
'''Return all adjacent tiles to this tile.'''
adj = [ d.offset for d in direction_by_abr.values()]
return [t for t in [self.get((tile.x + idx[0],tile.y + idx[1])) for idx in adj] if t]
