def create_water(ai_settings, screen, waters, water_number, list_number):
'''创建一个外星人并将其放在当前行'''
water = Water(ai_settings, screen)
water_height = water.rect.height
water.y = water.rect.height + 2 * water.rect.height * water_number
water.rect.y = water.y
water.rect.x = water.rect.width + 2 * water.rect.width * list_number
waters.add(water)
