Improper yield

def draw():
    draw = tcod.console_put_char_ex
    w, h = screen_size()
    for x in range(w):
        for y in range(h):
            c, fg, bg = yield cartesian.Point(x, y)
            fg, bg = (getattr(tcod, str(fg), tcod.white),
                      getattr(tcod, str(bg), tcod.black))
            draw(None, x, y, c, fg, bg)
    yield None


# Outside the generator
def render(self):
    draw = render.draw()
    point = draw.send(None)
    world = self.world
    while point:
        world_coord = self.camera.position + point
        tile_data = ('.', 'red', 'blue')
        if world_coord in world:
            tile = world[world_coord]
            tile_data = (tile.repr, tile.fg, tile.bg)
        point = draw.send(tile_data)