求助帖。。。Python武装飞船里，setting类报错AttributeError: 'Settings' object has no attribute '

class Settings():
    def __init__(self):
        self.screen_width = 1200
        self.screen_height = 800
        self.bg_color = (230,230,230)

import sys
import pygame
from settings import Settings
def run_game():
    #初始化一个游戏并且创建一个屏幕
    pygame.init()
    ai_settings=Settings()
    print(ai_settings.screen_height)
    screen=pygame.display.set_mode((ai_settings.screen_width,ai_settings.screen_height))
    pygame.display.set_caption("Alien Invasion")
    #开始游戏的主循环
    while True:
         #监视键盘鼠标
        for event in pygame.event.get():
            if event.type==pygame.QUIT:
                sys.exit()
        #每次循环时都从新绘制屏幕
        screen.fill(ai_settings.bg_color)
        #让最近的屏幕绘制可见
        pygame.display.flip()
run_game()