python中有关类的属性的问题,请帮我看看哪里导致编译错误

#主程序
import sys

import pygame
from settings import Settings
from ship import Ship

def run_game():
    pygame.init()
    ai_settings = Settings()
    screen = pygame.display.set_mode(ai_settings.screen_width,ai_settings.screen_height)  
    pygame.display.set_caption("Alien Invasion")
    
    """buiding a ship"""         
    ship = Ship(screen)        

    while True:
        for event in pygame.event.get():
            if event.type == pygame.QUIT:
                sys.exit()
        screen.fill(ai_settings.bg_color)
        ship.blitme()
        pygame.display.flip()

run_game()


#设置类,说我类中没有相应属性
class Settings():
    def _init_(self):
        self.screen_width = 1200
        self.screen_height = 800
        self.bg_color = (230,230,230)

运行报错原因:

Traceback (most recent call last):
  File "E:\Alien_invasion\alien_invasion.py",  in <module>
    run_game()
  File "E:\Alien_invasion\alien_invasion.py",in run_game
    screen = pygame.display.set_mode(ai_settings.screen_width,ai_settings.screen_height)
AttributeError: 'Settings' object has no attribute 'screen_width'

我明明定义了了属性'screen_width'，为什么还报错呢？

ai_settings.screen_width,ai_settings.screen_height    
这里改成下面的代码试下
ai_settings.self.screen_width,ai_settings.self.screen_height