Scrapy:In a request fails (eg 404,500), how to ask

问题:

I have a problem with scrapy. In a request fails (eg 404,500), how to ask for another alternative request? Such as two links can obtain price info, the one failed, request another automatically.

回答1:

Use "errback" in the Request like errback=self.error_handler where error_handler is a function (just like callback function) in this function check the error code and make the alternative Request.

see errback in the scrapy documentation: http://doc.scrapy.org/en/latest/topics/request-response.html

回答2:

Just set handle_httpstatus_list = [404, 500] and check for the status code in parse method. Here's an example:

from scrapy.http import Request
from scrapy.spider import BaseSpider


class MySpider(BaseSpider):
    handle_httpstatus_list = [404, 500]
    name = "my_crawler"

    start_urls = ["http://github.com/illegal_username"]

    def parse(self, response):
        if response.status in self.handle_httpstatus_list:
            return Request(url="https://github.com/kennethreitz/", callback=self.after_404)

    def after_404(self, response):
        print response.url

        # parse the page and extract items

Also see:

• How to get the scrapy failure URLs?
• Scrapy and response status code: how to check against it?
• How to retry for 404 link not found in scrapy?

Hope that helps.