爬虫中遇到的问题Crawled (404)，[scrapy.spidermiddlewares.offsite] DEBUG: Filtered offsite request to

1.错误1：url地址有误

Crawled (200) (referer: None)
DEBUG: Crawled (404) (referer: None)

解决：复制url的完全地址

start_urls = ['http://www.itcast.cn/channel/teacher.shtml/']  # 刚开始的url
start_urls = ['http://www.itcast.cn/channel/teacher.shtml#ajavaee']  # 改了之后的url

2.错误2：[scrapy.spidermiddlewares.offsite] DEBUG: Filtered offsite request to

解决：dont_filter=True

yield scrapy.Request(
    item["s_href"],
    callback=self.parse_book_list,
    meta={"item": deepcopy(item)},
    dont_filter=True
)