scrapy：蜘蛛中的一个小“蜘蛛”？

Question

因此，当我尝试从epinions.com抓取产品评论信息时，如果主要评论文本过长，则它具有指向其他页面的“更多信息”链接。 我从“ http://www.epinions.com/reviews/samsung-galaxy-note-16-gb-cell-phone/pa_~1 ”中举了一个例子，如果您看第一篇评论，您会明白我的意思。 。

我想知道：是否可能在for循环的每次迭代中都有一个小蜘蛛来抓取URL并将评论从新链接中删除？ 我有以下代码，但不适用于微小的“蜘蛛”。

这是我的代码：

from scrapy.spider import BaseSpider
from scrapy.selector import HtmlXPathSelector
from epinions_test.items import EpinionsTestItem
from scrapy.http import Response, HtmlResponse

class MySpider(BaseSpider):
    name = "epinions"
    allow_domains = ["epinions.com"]
    start_urls = ['http://www.epinions.com/reviews/samsung-galaxy-note-16-gb-cell-phone/pa_~1']

    def parse(self, response):
        hxs = HtmlXPathSelector(response)
        sites = hxs.select('//div[@class="review_info"]')

        items = []
        for sites in sites:
            item = EpinionsTestItem()
            item["title"] = sites.select('h2/a/text()').extract()
            item["star"] = sites.select('span/a/span/@title').extract()
            item["date"] = sites.select('span/span/span/@title').extract()
            item["review"] = sites.select('p/span/text()').extract()
# Everything works fine and i do have those four columns beautifully printed out, until....

            url2 = sites.select('p/span/a/@href').extract()
            url = str("http://www.epinions.com%s" %str(url2)[3:-2])
# This url is a string. when i print it out, it's like "http://www.epinions.com/review/samsung-galaxy-note-16-gb-cell-phone/content_624031731332", which looks legit.

            response2 = HtmlResponse(url)
# I tried in a scrapy shell, it shows that this is a htmlresponse...

            hxs2 = HtmlXPathSelector(response2)
            fullReview = hxs2.select('//div[@class = "user_review_full"]')
            item["url"] = fullReview.select('p/text()').extract()
# The three lines above works in an independent spider, where start_url is changed to the url just generated and everything.
# However, i got nothing from item["url"] in this code.

            items.append(item)
        return items

为什么item [“ url”]不返回任何内容？

谢谢！

Answer 1

您应该在回调中实例化一个新的Request并在meta dict中传递您的item ：

from scrapy.http import Request
from scrapy.item import Item, Field
from scrapy.spider import BaseSpider
from scrapy.selector import HtmlXPathSelector


class EpinionsTestItem(Item):
    title = Field()
    star = Field()
    date = Field()
    review = Field()


class MySpider(BaseSpider):
    name = "epinions"
    allow_domains = ["epinions.com"]
    start_urls = ['http://www.epinions.com/reviews/samsung-galaxy-note-16-gb-cell-phone/pa_~1']

    def parse(self, response):
        hxs = HtmlXPathSelector(response)
        sites = hxs.select('//div[@class="review_info"]')

        for sites in sites:
            item = EpinionsTestItem()
            item["title"] = sites.select('h2/a/text()').extract()
            item["star"] = sites.select('span/a/span/@title').extract()
            item["date"] = sites.select('span/span/span/@title').extract()

            url = sites.select('p/span/a/@href').extract()
            url = str("http://www.epinions.com%s" % str(url)[3:-2])

            yield Request(url=url, callback=self.parse_url2, meta={'item': item})

    def parse_url2(self, response):
        hxs = HtmlXPathSelector(response)

        item = response.meta['item']
        fullReview = hxs.select('//div[@class = "user_review_full"]')
        item["review"] = fullReview.select('p/text()').extract()
        yield item

另请参阅文档 。

希望能有所帮助。