python - Scrapy不同数量的url返回

Question

我已经为固定域内的爬虫构建了一个爬虫，并提取与修复正则表达式匹配的 url。如果看到特定的 url，爬虫就会跟踪该链接。爬虫可以完美地提取 url，但每次我运行爬虫时，它都会返回不同数量的链接，即每次运行时链接的数量都不同。我正在使用 Scrapy 进行抓取。这是 scrapy 的问题吗？代码是:

class MySpider(CrawlSpider):
   name = "xyz"
   allowed_domains = ["xyz.nl"]
   start_urls = ["http://www.xyz.nl/Vacancies"] 
   rules = (Rule(SgmlLinkExtractor(allow=[r'\/V-\d{7}\/[\w\S]+']), callback='parse_item'),Rule(SgmlLinkExtractor(allow=[r'\?page\=\d+\&sortCriteria\=1']), follow=True),)



 def parse_item(self, response):

  outputfile = open('urllist.txt','a')
  print response.url
  outputfile.write(response.url+'\n')

Answer 1

与其手动编写链接并在 parse_item() 方法中使用 a 模式打开文件，不如使用 scrapy 的内置 item exporters .定义一个带有链接字段的项目:

from scrapy.contrib.linkextractors.sgml import SgmlLinkExtractor
from scrapy.contrib.spiders import CrawlSpider, Rule
from scrapy.item import Item, Field


class MyItem(Item):
    url = Field()


class MySpider(CrawlSpider):
    name = "xyz"
    allowed_domains = ["xyz.nl"]
    start_urls = ["http://www.xyz.nl/Vacancies"]
    rules = (Rule(SgmlLinkExtractor(allow=[r'\/V-\d{7}\/[\w\S]+']), callback='parse_item'),
             Rule(SgmlLinkExtractor(allow=[r'\?page\=\d+\&sortCriteria\=1']), follow=True),)

    def parse_item(self, response):
        item = MyItem()
        item['url'] = response.url
        yield item