嘤

snake.velocity = Point(0,-1)print(snake.velocity)print(Point(0,-1))print(snake.velocity == Point(0,-1))    #FALSE，因为Point(0,-1)每次都是一个新地址aaa = Point(0,-1)snake.velocity = aaaprint(snake.velocity == Point(0,-1))    #FALSE，因为Point(0,-1)每次都是一个新地址print(snake.velocity == aaa)      　　　 #TRUE，因为aaa固定了地址，snake.velocity指向的刚好是aaa指向的地址