Question

我正在尝试从使用__doPostBack功能的网站上搜索搜索结果。该网页每个搜索查询显示10个结果。要查看更多结果，必须单击触发__doPostBack javascript的按钮。经过一些研究，我意识到POST请求的行为就像一个表单，并且可以简单地使用scrapy＆＃39; FormRequest来填充该表单。我使用了以下主题：

Troubles using scrapy with javascript __doPostBack method

编写以下脚本。

# -*- coding: utf-8 -*- 
from scrapy.contrib.spiders import CrawlSpider
from scrapy.http import FormRequest
from scrapy.http import Request
from scrapy.selector import Selector
from ahram.items import AhramItem
import re

class MySpider(CrawlSpider):
    name = u"el_ahram2"

    def start_requests(self):
        search_term = u'اقتصاد'
        baseUrl = u'http://digital.ahram.org.eg/sresult.aspx?srch=' + search_term + u'&archid=1'
        requests = []
        for i in range(1, 4):#crawl first 3 pages as a test
            argument =  u"'Page$"+ str(i+1) + u"'"
            data = {'__EVENTTARGET': u"'GridView1'", '__EVENTARGUMENT': argument}
            currentPage = FormRequest(baseUrl, formdata = data, callback = self.fetch_articles)
            requests.append(currentPage)
        return requests

    def fetch_articles(self, response):
        sel = Selector(response)
        for ref in sel.xpath("//a[contains(@href,'checkpart.aspx?Serial=')]/@href").extract(): 
            yield Request('http://digital.ahram.org.eg/' + ref, callback=self.parse_items)

    def parse_items(self, response):
        sel = Selector(response)
        the_title = ' '.join(sel.xpath("//title/text()").extract()).replace('\n','').replace('\r','').replace('\t','')#* mean 'anything'
        the_authors = '---'.join(sel.xpath("//*[contains(@id,'editorsdatalst_HyperLink')]//text()").extract())
        the_text = ' '.join(sel.xpath("//span[@id='TextBox2']/text()").extract())
        the_month_year = ' '.join(sel.xpath("string(//span[@id = 'Label1'])").extract())
        the_day = ' '.join(sel.xpath("string(//span[@id = 'Label2'])").extract())
        item = AhramItem()
        item["Authors"] = the_authors
        item["Title"] = the_title
        item["MonthYear"] = the_month_year
        item["Day"] = the_day
        item['Text'] = the_text
        return item

我现在的问题是＆＃39; fetch_articles＆＃39;永远不会被称为：

2014-05-27 12:19:12+0200 [scrapy] DEBUG: Web service listening on 0.0.0.0:6080
2014-05-27 12:19:13+0200 [el_ahram2] DEBUG: Crawled (200) <POST     http://digital.ahram.org.eg/sresult.aspx?srch=%D8%A7%D9%82%D8%AA%D8%B5%D8%A7%D8%AF&archid=1> (referer: None)
2014-05-27 12:19:13+0200 [el_ahram2] DEBUG: Crawled (200) <POST http://digital.ahram.org.eg/sresult.aspx?srch=%D8%A7%D9%82%D8%AA%D8%B5%D8%A7%D8%AF&archid=1> (referer: None)
2014-05-27 12:19:13+0200 [el_ahram2] DEBUG: Crawled (200) <POST http://digital.ahram.org.eg/sresult.aspx?srch=%D8%A7%D9%82%D8%AA%D8%B5%D8%A7%D8%AF&archid=1> (referer: None)
2014-05-27 12:19:13+0200 [el_ahram2] INFO: Closing spider (finished)

经过几天的搜索，我觉得完全卡住了。我是python的初学者，所以错误也许是微不足道的。但是，如果不是这样，该线程可能对许多人有用。提前感谢您的帮助。

Answer 1

你的代码很好。 fetch_articles正在运行。您可以通过添加打印语句来测试它。

但是，该网站要求您验证POST请求。为了验证它们，您的请求正文中必须有__EVENTVALIDATION和__VIEWSTATE来证明您正在回复其表单。为了获得这些，您需要首先发出GET请求，然后从表单中提取这些字段。如果你不提供这个，你会得到一个错误页面，它不包含任何带有“checkpart.aspx？Serial =”的链接，所以你的for循环没有被执行。

以下是我设置start_request的方式，然后fetch_search完成start_request以前的工作。

class MySpider(CrawlSpider):
    name = u"el_ahram2"

    def start_requests(self):
        search_term = u'اقتصاد'
        baseUrl = u'http://digital.ahram.org.eg/sresult.aspx?srch=' + search_term + u'&archid=1'
        SearchPage = Request(baseUrl, callback = self.fetch_search)
        return [SearchPage]

    def fetch_search(self, response):
        sel = Selector(response)
        search_term = u'اقتصاد'
        baseUrl = u'http://digital.ahram.org.eg/sresult.aspx?srch=' + search_term + u'&archid=1'
        viewstate = sel.xpath("//input[@id='__VIEWSTATE']/@value").extract().pop()
        eventvalidation = sel.xpath("//input[@id='__EVENTVALIDATION']/@value").extract().pop()
        for i in range(1, 4):#crawl first 3 pages as a test
            argument =  u"'Page$"+ str(i+1) + u"'"
            data = {'__EVENTTARGET': u"'GridView1'", '__EVENTARGUMENT': argument, '__VIEWSTATE': viewstate, '__EVENTVALIDATION': eventvalidation}
            currentPage = FormRequest(baseUrl, formdata = data, callback = self.fetch_articles)
            yield currentPage

    ...

Answer 2

 def fetch_articles(self, response):
    sel = Selector(response)
    print response._get_body() # you can write to file and do an grep 
    for ref in sel.xpath("//a[contains(@href,'checkpart.aspx?Serial=')]/@href").extract(): 
        yield Request('http://digital.ahram.org.eg/' + ref, callback=self.parse_items)

我找不到＆＃34; checkpart.aspx？Serial =＆＃34;你正在寻找。

这可能无法解决您的问题，但使用答案代替代码格式的注释。

使用链接网址隐藏的__doPostBack进行刮擦

2 个答案: