按顺序抓取 URL

问题描述

所以，我的问题比较简单.我有一个爬虫爬取多个站点，我需要它按照我在代码中编写的顺序返回数据.贴在下面.

So, my problem is relatively simple. I have one spider crawling multiple sites, and I need it to return the data in the order I write it in my code. It's posted below.

from scrapy.spider import BaseSpider
from scrapy.selector import HtmlXPathSelector
from mlbodds.items import MlboddsItem

class MLBoddsSpider(BaseSpider):
   name = "sbrforum.com"
   allowed_domains = ["sbrforum.com"]
   start_urls = [
       "http://www.sbrforum.com/mlb-baseball/odds-scores/20110328/",
       "http://www.sbrforum.com/mlb-baseball/odds-scores/20110329/",
       "http://www.sbrforum.com/mlb-baseball/odds-scores/20110330/"
   ]

   def parse(self, response):
       hxs = HtmlXPathSelector(response)
       sites = hxs.select('//div[@id="col_3"]//div[@id="module3_1"]//div[@id="moduleData4952"]')
       items = []
       for site in sites:
           item = MlboddsItem()
           item['header'] = site.select('//div[@class="scoreboard-bar"]//h2//span[position()>1]//text()').extract()# | /*//table[position()<2]//tr//th[@colspan="2"]//text()').extract()
           item['game1'] = site.select('/*//table[position()=1]//tr//td[@class="tbl-odds-c2"]//text() | /*//table[position()=1]//tr//td[@class="tbl-odds-c4"]//text() | /*//table[position()=1]//tr//td[@class="tbl-odds-c6"]//text()').extract()
           items.append(item)
       return items

结果以随机顺序返回，例如返回第 29 个，然后是第 28 个，然后是第 30 个.我尝试将调度程序顺序从 DFO 更改为 BFO，以防万一出现问题，但这并没有改变任何东西.

The results are returned in a random order, for example it returns the 29th, then the 28th, then the 30th. I've tried changing the scheduler order from DFO to BFO, just in case that was the problem, but that didn't change anything.

推荐答案

start_urls 定义在 start_requests 方法.下载页面时，您的 parse 方法会调用每个起始 URL 的响应.但是你无法控制加载时间——第一个开始 url 可能会在 parse 的最后一个.

start_urls defines urls which are used in start_requests method. Your parse method is called with a response for each start urls when the page is downloaded. But you cannot control loading times - the first start url might come the last to parse.

一种解决方案——覆盖 start_requests 方法，并在生成的请求中添加一个带有 priority 键的 meta.在 parse 中提取此 priority 值并将其添加到 item.在管道中根据这个值做一些事情.(我不知道为什么以及在哪里需要按此顺序处理这些 url).

A solution -- override start_requests method and add to generated requests a meta with priority key. In parse extract this priority value and add it to the item. In the pipeline do something based in this value. (I don't know why and where you need these urls to be processed in this order).

或者让它同步——将这些起始网址存储在某个地方.将 start_urls 放入其中的第一个.在 parse 中处理第一个响应并生成项目，然后从您的存储中获取下一个 url 并使用 parse 的回调对其发出​​请求.

Or make it kind of synchronous -- store these start urls somewhere. Put in start_urls the first of them. In parse process the first response and yield the item(s), then take next url from your storage and make a request for it with callback for parse.

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