python - 为什么我直接用requests爬网页可以，但用scrapy不行？

Question

class job51():
    def __init__(self):
        self.headers={
   'Accept': 'text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8',
    'Accept-Encoding':'gzip, deflate, sdch',
   'Accept-Language': 'zh-CN,zh;q=0.8',
    'Cache-Control': 'max-age=0',
   'User-Agent':'Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/54.0.2840.71 Safari/537.36',
    'Cookie':''
}

    def start(self):
        html=session.get("http://my.51job.com/cv/CResume/CV_CResumeManage.php",headers=self.headers)
        self.parse(html)

    def parse(self,response):
        tree=lxml.etree.HTML(response.text)
        resume_url=tree.xpath('//tbody/tr[@class="resumeName"]/td[1]/a/@href')
        print (resume_url[0]

能爬到我想要的结果，就是简历的url,但是用scrapy,同样的headers,页面好像停留在登录页面？

class job51(Spider):
    name = "job51"
    #allowed_domains = ["my.51job.com"]
    start_urls = ["http://my.51job.com/cv/CResume/CV_CResumeManage.php"]
    headers={
   'Accept': 'text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8',
    'Accept-Encoding':'gzip, deflate, sdch',
   'Accept-Language': 'zh-CN,zh;q=0.8',
    'Cache-Control': 'max-age=0',
   'User-Agent':'Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/54.0.2840.71 Safari/537.36',
    'Cookie':''
}

    def start_requests(self):
        yield  Request(url=self.start_urls[0],headers=self.headers,callback=self.parse)

    def parse(self,response):
        #tree=lxml.etree.HTML(text)
        selector=Selector(response)
        print ("<<<<<<<<<<<<<<<<<<<<<",response.text)
        resume_url=selector.xpath('//tr[@class="resumeName"]/td[1]/a/@href')
        print (">>>>>>>>>>>>",resume_url)

输出的结果：

scrapy.utils.log] INFO: Overridden settings: {'BOT_NAME': 'job51', 'SPIDER_MODULES': ['job51.spiders'], 'ROBOTSTXT_OBEY': True, 'NEWSPIDER_MODULE': 'job51.spiders'}
2017-04-11 10:58:31 [scrapy.middleware] INFO: Enabled extensions:
['scrapy.extensions.logstats.LogStats',
 'scrapy.extensions.corestats.CoreStats',
 'scrapy.extensions.telnet.TelnetConsole']
2017-04-11 10:58:32 [scrapy.middleware] INFO: Enabled downloader middlewares:
['scrapy.downloadermiddlewares.robotstxt.RobotsTxtMiddleware',
 'scrapy.downloadermiddlewares.httpauth.HttpAuthMiddleware',
 'scrapy.downloadermiddlewares.downloadtimeout.DownloadTimeoutMiddleware',
 'scrapy.downloadermiddlewares.defaultheaders.DefaultHeadersMiddleware',
 'scrapy.downloadermiddlewares.useragent.UserAgentMiddleware',
 'scrapy.downloadermiddlewares.retry.RetryMiddleware',
 'scrapy.downloadermiddlewares.redirect.MetaRefreshMiddleware',
 'scrapy.downloadermiddlewares.httpcompression.HttpCompressionMiddleware',
 'scrapy.downloadermiddlewares.redirect.RedirectMiddleware',
 'scrapy.downloadermiddlewares.cookies.CookiesMiddleware',
 'scrapy.downloadermiddlewares.stats.DownloaderStats']
2017-04-11 10:58:32 [scrapy.middleware] INFO: Enabled spider middlewares:
['scrapy.spidermiddlewares.httperror.HttpErrorMiddleware',
 'scrapy.spidermiddlewares.offsite.OffsiteMiddleware',
 'scrapy.spidermiddlewares.referer.RefererMiddleware',
 'scrapy.spidermiddlewares.urllength.UrlLengthMiddleware',
 'scrapy.spidermiddlewares.depth.DepthMiddleware']
2017-04-11 10:58:32 [scrapy.middleware] INFO: Enabled item pipelines:
[]
2017-04-11 10:58:32 [scrapy.core.engine] INFO: Spider opened
2017-04-11 10:58:32 [scrapy.extensions.logstats] INFO: Crawled 0 pages (at 0 pages/min), scraped 0 items (at 0 items/min)
2017-04-11 10:58:32 [scrapy.extensions.telnet] DEBUG: Telnet console listening on 127.0.0.1:6023
2017-04-11 10:58:33 [scrapy.core.engine] DEBUG: Crawled (404) <GET http://my.51job.com/robots.txt> (referer: None)
2017-04-11 10:58:33 [scrapy.core.engine] DEBUG: Crawled (200) <GET http://my.51job.com/cv/CResume/CV_CResumeManage.php> (referer: None)
<<<<<<<<<<<<<<<<<<<<< <script>window.location='https://login.51job.com/login.php?url=http://my.51job.com%2Fcv%2FCResume%2FCV_CResumeManage.php%3F7087';</script>
>>>>>>>>>>>> []
2017-04-11 10:58:33 [scrapy.core.scraper] ERROR: Spider error processing <GET http://my.51job.com/cv/CResume/CV_CResumeManage.php> (referer: None)
Traceback (most recent call last):
  File "d:\python35\lib\site-packages\scrapy\utils\defer.py", line 102, in iter_errback
    yield next(it)
  File "d:\python35\lib\site-packages\scrapy\spidermiddlewares\offsite.py", line 29, in process_spider_output
    for x in result:
  File "d:\python35\lib\site-packages\scrapy\spidermiddlewares\referer.py", line 22, in <genexpr>
    return (_set_referer(r) for r in result or ())
  File "d:\python35\lib\site-packages\scrapy\spidermiddlewares\urllength.py", line 37, in <genexpr>
    return (r for r in result or () if _filter(r))
  File "d:\python35\lib\site-packages\scrapy\spidermiddlewares\depth.py", line 58, in <genexpr>
    return (r for r in result or () if _filter(r))
  File "E:\WorkGitResp\spider\job51\job51\spiders\51job_resume.py", line 43, in parse
    yield Request(resume_url[0],headers=self.headers,callback=self.getResume)
  File "d:\python35\lib\site-packages\parsel\selector.py", line 58, in __getitem__
    o = super(SelectorList, self).__getitem__(pos)
IndexError: list index out of range
2017-04-11 10:58:33 [scrapy.core.engine] INFO: Closing spider (finished)
2017-04-11 10:58:33 [scrapy.statscollectors] INFO: Dumping Scrapy stats:
{'downloader/request_bytes': 628,
 'downloader/request_count': 2,
 'downloader/request_method_count/GET': 2,
 'downloader/response_bytes': 5743,
 'downloader/response_count': 2,
 'downloader/response_status_count/200': 1,
 'downloader/response_status_count/404': 1,
 'finish_reason': 'finished',
 'finish_time': datetime.datetime(2017, 4, 11, 2, 58, 33, 275634),
 'log_count/DEBUG': 3,
 'log_count/ERROR': 1,
 'log_count/INFO': 7,
 'response_received_count': 2,
 'scheduler/dequeued': 1,
 'scheduler/dequeued/memory': 1,
 'scheduler/enqueued': 1,
 'scheduler/enqueued/memory': 1,
 'spider_exceptions/IndexError': 1,
 'start_time': datetime.datetime(2017, 4, 11, 2, 58, 32, 731603)}
2017-04-11 10:58:33 [scrapy.core.engine] INFO: Spider closed (finished)

Answer 1

看log是404了，你看看scrapy设定那里有没把重定向禁止了。

Answer 2

<script>window.location='https://login.51job.com/login.php?url=http://my.51job.com%2Fcv%2FCResume%2FCV_CResumeManage.php%3F7087';</script>

从这里可以看到你用scrapy写的爬虫被重定向到登陆页面了。所以会报错。建议你在用requests和用scrapy请求的时候抓一下包，看看它的响应内容，并且看看它们的request headers是不是完全相同。我怀疑可能是cookie过期了，要么scrapy可能不是这样传cookie.我对scrapy不是特别熟悉，不过看问题应该是出在cookie这块了

Answer 3

你用的session请求的，实际的request header估计已经戴上了cookie了，所以还是像楼上说的对比请求header吧