scrapy：蜘蛛中的小“蜘蛛”？

Question

所以当我尝试从epinions.com 抓取产品评论信息时，如果主要评论文本太长，它会有一个“阅读更多”链接到另一个页面。 我从“http://www.epinions.com/reviews/samsung-galaxy-note-16-gb-cell-phone/pa_~1”中举了一个例子，如果您查看第一条评论，您就会明白我的意思。

我想知道：是否有可能在 for 循环的每次迭代中都有一个小蜘蛛来抓取 url 并从新链接中删除评论？我有以下代码，但它不适用于微小的“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"] 什么都不返回？

谢谢！

Answer 1

您应该在回调中实例化一个新的Request，并在meta 字典中传递您的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

另见documentation。

希望对您有所帮助。