Scrapy规则如何与爬行蜘蛛一起使用

我构建的rule/regex将是:

Rule(SgmlLinkExtractor(allow=('seasoncode\=E\d+\&gamenumber\=\d+\&phasetypecode\=\w+',)),follow=True),

第3步

现在我到达页面(http://www.euroleague.net/main/results/by-date?seasoncode=E2001&gamenumber=1&phasetypecode=RS)我准备提取链接,这些链接指向包含我需要的所有信息的页面:我正在寻找HTML/href:

href="/main/results/showgame?gamenumber=1&phasetypecode=RS&gamecode=4&seasoncode=E2001#!boxscore"

我必须遵循的正则表达式是:

Rule(SgmlLinkExtractor(allow=('gamenumber\=\d+\&phasetypecode\=\w+\&gamecode\=\d+\&seasoncode\=E\d+',)),callback='parse_item'),

问题

我认为爬虫应该像这样工作:规则爬虫就像一个循环.当第一个链接匹配时,爬虫将跟随"步骤2"页面,而不是"步骤3",之后它将提取数据.执行此操作后,它将返回"步骤1"以匹配第二个链接并再次开始循环到第一步中没有链接的点.

我从终端看到的似乎是爬虫在"步骤1"中循环.它遍历所有"步骤1"链接,但不涉及"步骤2"/"步骤3"规则.

2014-02-28 00:20:31+0200 [basketsp_test] DEBUG: Crawled (200)  (referer: http://  www.euroleague.net/main/results/by-date)
2014-02-28 00:20:31+0200 [basketsp_test] DEBUG: Crawled (200)  (referer: http://www.euroleague.net/main/results/by-date)
2014-02-28 00:20:31+0200 [basketsp_test] DEBUG: Crawled (200)  (referer: http://www.euroleague.net/main/results/by-date)
2014-02-28 00:20:32+0200 [basketsp_test] DEBUG: Crawled (200)  (referer: http://www.euroleague.net/main/results/by-date)
2014-02-28 00:20:33+0200 [basketsp_test] DEBUG: Crawled (200)  (referer: http://www.euroleague.net/main/results/by-date)

在它遍历所有"季节"链接后,它以我看不到的链接开始,在我提到的三个步骤中的任何一个:

http://www.euroleague.net/main/results/by-date?gamenumber=23&phasetypecode=TS++++++++&seasoncode=E2013

只有当您循环遍历"步骤2"中的所有链接而不返回"步骤1"起点时,才能找到这样的链接结构.

问题是: 规则如何运作？它是否一步一步地工作,就像我打算它应该与这个例子一起工作,或者每个规则都有它自己的循环,并且只有在完成第一个规则的循环之后才从规则到规则？

这就是我看到它的方式.当然,我的规则/正则表达式可能有问题,而且非常有可能.

以下是我从终端获得的所有信息:

scrapy crawl basketsp_test -o item6.xml -t xml
2014-02-28 01:09:20+0200 [scrapy] INFO: Scrapy 0.20.0 started (bot: basketbase)
2014-02-28 01:09:20+0200 [scrapy] DEBUG: Optional features available: ssl, http11, boto, django
2014-02-28 01:09:20+0200 [scrapy] DEBUG: Overridden settings: {'NEWSPIDER_MODULE': 'basketbase.spiders', 'FEED_FORMAT': 'xml', 'SPIDER_MODULES': ['basketbase.spiders'], 'FEED_URI': 'item6.xml', 'BOT_NAME': 'basketbase'}
2014-02-28 01:09:21+0200 [scrapy] DEBUG: Enabled extensions: FeedExporter, LogStats, TelnetConsole, CloseSpider, WebService, CoreStats, SpiderState
2014-02-28 01:09:21+0200 [scrapy] DEBUG: Enabled downloader middlewares: HttpAuthMiddleware, DownloadTimeoutMiddleware, UserAgentMiddleware, RetryMiddleware, DefaultHeadersMiddleware, MetaRefreshMiddleware, HttpCompressionMiddleware, RedirectMiddleware, CookiesMiddleware, ChunkedTransferMiddleware, DownloaderStats
2014-02-28 01:09:21+0200 [scrapy] DEBUG: Enabled spider middlewares: HttpErrorMiddleware, OffsiteMiddleware, RefererMiddleware, UrlLengthMiddleware, DepthMiddleware
2014-02-28 01:09:21+0200 [scrapy] DEBUG: Enabled item pipelines: Basketpipeline3, Basketpipeline1db
2014-02-28 01:09:21+0200 [basketsp_test] INFO: Spider opened
2014-02-28 01:09:21+0200 [basketsp_test] INFO: Crawled 0 pages (at 0 pages/min), scraped 0 items (at 0 items/min)
2014-02-28 01:09:21+0200 [scrapy] DEBUG: Telnet console listening on 0.0.0.0:6023
2014-02-28 01:09:21+0200 [scrapy] DEBUG: Web service listening on 0.0.0.0:6080
2014-02-28 01:09:21+0200 [basketsp_test] DEBUG: Crawled (200)  (referer: None)
2014-02-28 01:09:22+0200 [basketsp_test] DEBUG: Crawled (200)  (referer: http://www.euroleague.net/main/results/by-date)
2014-02-28 01:09:22+0200 [basketsp_test] DEBUG: Filtered duplicate request:  - no more duplicates will be shown (see DUPEFILTER_CLASS)
2014-02-28 01:09:22+0200 [basketsp_test] DEBUG: Crawled (200)  (referer: http://www.euroleague.net/main/results/by-date)
2014-02-28 01:09:23+0200 [basketsp_test] DEBUG: Crawled (200)  (referer: http://www.euroleague.net/main/results/by-date)
2014-02-28 01:09:23+0200 [basketsp_test] DEBUG: Crawled (200)  (referer: http://www.euroleague.net/main/results/by-date)
2014-02-28 01:09:24+0200 [basketsp_test] DEBUG: Crawled (200)  (referer: http://www.euroleague.net/main/results/by-date)
2014-02-28 01:09:24+0200 [basketsp_test] DEBUG: Crawled (200)  (referer: http://www.euroleague.net/main/results/by-date)
2014-02-28 01:09:25+0200 [basketsp_test] DEBUG: Crawled (200)  (referer: http://www.euroleague.net/main/results/by-date)
2014-02-28 01:09:26+0200 [basketsp_test] DEBUG: Crawled (200)  (referer: http://www.euroleague.net/main/results/by-date)
2014-02-28 01:09:26+0200 [basketsp_test] DEBUG: Crawled (200)  (referer: http://www.euroleague.net/main/results/by-date)
2014-02-28 01:09:27+0200 [basketsp_test] DEBUG: Crawled (200)  (referer: http://www.euroleague.net/main/results/by-date)
2014-02-28 01:09:27+0200 [basketsp_test] DEBUG: Crawled (200)  (referer: http://www.euroleague.net/main/results/by-date)
2014-02-28 01:09:28+0200 [basketsp_test] DEBUG: Crawled (200)  (referer: http://www.euroleague.net/main/results/by-date)
2014-02-28 01:09:29+0200 [basketsp_test] DEBUG: Crawled (200)  (referer: http://www.euroleague.net/main/results/by-date)
2014-02-28 01:09:29+0200 [basketsp_test] DEBUG: Crawled (200)  (referer: http://www.euroleague.net/main/results/by-date)
2014-02-28 01:09:30+0200 [basketsp_test] DEBUG: Crawled (200)  (referer: http://www.euroleague.net/main/results/by-date?seasoncode=E2013)
2014-02-28 01:09:30+0200 [basketsp_test] DEBUG: Crawled (200)  (referer: http://www.euroleague.net/main/results/by-date?seasoncode=E2013)
2014-02-28 01:09:31+0200 [basketsp_test] DEBUG: Crawled (200)  (referer: http://www.euroleague.net/main/results/by-date?seasoncode=E2013)
2014-02-28 01:09:32+0200 [basketsp_test] DEBUG: Crawled (200)  (referer: http://www.euroleague.net/main/results/by-date?seasoncode=E2013)
2014-02-28 01:09:32+0200 [basketsp_test] DEBUG: Crawled (200)  (referer: http://www.euroleague.net/main/results/by-date?seasoncode=E2013)
2014-02-28 01:09:33+0200 [basketsp_test] DEBUG: Crawled (200)  (referer: http://www.euroleague.net/main/results/by-date?seasoncode=E2013)
2014-02-28 01:09:34+0200 [basketsp_test] DEBUG: Crawled (200)  (referer: http://www.euroleague.net/main/results/by-date?seasoncode=E2013)
2014-02-28 01:09:34+0200 [basketsp_test] DEBUG: Crawled (200)  (referer: http://www.euroleague.net/main/results/by-date?seasoncode=E2013)
2014-02-28 01:09:35+0200 [basketsp_test] DEBUG: Crawled (200)  (referer: http://www.euroleague.net/main/results/by-date?seasoncode=E2013)
2014-02-28 01:09:35+0200 [basketsp_test] DEBUG: Crawled (200)  (referer: http://www.euroleague.net/main/results/by-date?seasoncode=E2013)
2014-02-28 01:09:36+0200 [basketsp_test] DEBUG: Crawled (200)  (referer: http://www.euroleague.net/main/results/by-date?seasoncode=E2013)
2014-02-28 01:09:37+0200 [basketsp_test] DEBUG: Crawled (200)  (referer: http://www.euroleague.net/main/results/by-date?seasoncode=E2013)
2014-02-28 01:09:37+0200 [basketsp_test] DEBUG: Crawled (200)  (referer: http://www.euroleague.net/main/results/by-date?seasoncode=E2013)
2014-02-28 01:09:38+0200 [basketsp_test] DEBUG: Crawled (200)  (referer: http://www.euroleague.net/main/results/by-date?seasoncode=E2013)
2014-02-28 01:09:39+0200 [basketsp_test] DEBUG: Crawled (200)  (referer: http://www.euroleague.net/main/results/by-date?seasoncode=E2013)
2014-02-28 01:09:39+0200 [basketsp_test] DEBUG: Crawled (200)  (referer: http://www.euroleague.net/main/results/by-date?seasoncode=E2013)
2014-02-28 01:09:40+0200 [basketsp_test] DEBUG: Crawled (200)  (referer: http://www.euroleague.net/main/results/by-date?seasoncode=E2013)
2014-02-28 01:09:40+0200 [basketsp_test] DEBUG: Crawled (200)  (referer: http://www.euroleague.net/main/results/by-date?seasoncode=E2013)
2014-02-28 01:09:41+0200 [basketsp_test] DEBUG: Crawled (200)  (referer: http://www.euroleague.net/main/results/by-date?seasoncode=E2013)
2014-02-28 01:09:42+0200 [basketsp_test] DEBUG: Crawled (200)  (referer: http://www.euroleague.net/main/results/by-date?seasoncode=E2013)
2014-02-28 01:09:42+0200 [basketsp_test] DEBUG: Crawled (200)  (referer: http://www.euroleague.net/main/results/by-date?seasoncode=E2013)
2014-02-28 01:09:43+0200 [basketsp_test] DEBUG: Crawled (200)  (referer: http://www.euroleague.net/main/results/by-date?seasoncode=E2013)
2014-02-28 01:09:44+0200 [basketsp_test] DEBUG: Crawled (200)  (referer: http://www.euroleague.net/main/results/by-date?seasoncode=E2013)
2014-02-28 01:09:44+0200 [basketsp_test] DEBUG: Crawled (200)  (referer: http://www.euroleague.net/main/results/by-date?seasoncode=E2013)
2014-02-28 01:09:44+0200 [basketsp_test] INFO: Closing spider (finished)
2014-02-28 01:09:44+0200 [basketsp_test] INFO: Dumping Scrapy stats:
    {'downloader/request_bytes': 13663,
     'downloader/request_count': 39,
     'downloader/request_method_count/GET': 39,
     'downloader/response_bytes': 527838,
     'downloader/response_count': 39,
     'downloader/response_status_count/200': 39,
     'finish_reason': 'finished',
     'finish_time': datetime.datetime(2014, 2, 27, 23, 9, 44, 569579),
     'log_count/DEBUG': 46,
     'log_count/INFO': 3,
     'request_depth_max': 2,
     'response_received_count': 39,
     'scheduler/dequeued': 39,
     'scheduler/dequeued/memory': 39,
     'scheduler/enqueued': 39,
     'scheduler/enqueued/memory': 39,
     'start_time': datetime.datetime(2014, 2, 27, 23, 9, 21, 111255)}
2014-02-28 01:09:44+0200 [basketsp_test] INFO: Spider closed (finished)

以下是爬虫的规则部分:

class Basketspider(CrawlSpider):
    name = "basketsp_test"
    download_delay = 0.5

    allowed_domains = ["www.euroleague.net"]
    start_urls = ["http://www.euroleague.net/main/results/by-date"]
    rules = (
        Rule(SgmlLinkExtractor(allow=('by-date\?seasoncode\=E\d+',)),follow=True),
        Rule(SgmlLinkExtractor(allow=('seasoncode\=E\d+\&gamenumber\=\d+\&phasetypecode\=\w+',)),follow=True),
        Rule(SgmlLinkExtractor(allow=('gamenumber\=\d+\&phasetypecode\=\w+\&gamecode\=\d+\&seasoncode\=E\d+',)),callback='parse_item'),



)  

user2016508.. 15

你是对的,根据源代码在将每个响应返回给回调函数之前,爬虫程序从第一个开始循环遍历规则.在编写规则时,您应该记住它.例如以下规则:

rules(
        Rule(SgmlLinkExtractor(allow=(r'/items',)), callback='parse_item',follow=True),
        Rule(SgmlLinkExtractor(allow=(r'/items/electronics',)), callback='parse_electronic_item',follow=True),
     )

永远不会应用第二条规则,因为第一条规则将使用parse_item回调提取所有链接.第二条规则的匹配将被过滤掉为重复项scrapy.dupefilter.RFPDupeFilter.你应该使用deny来正确匹配链接:

rules(
        Rule(SgmlLinkExtractor(allow=(r'/items',)), deny=(r'/items/electronics',), callback='parse_item',follow=True),
        Rule(SgmlLinkExtractor(allow=(r'/items/electronics',)), callback='parse_electronic_item',follow=True),
     )

宏杰李.. 8

如果你来自中国,我有一篇关于此的中文博客文章:

别再滥用scrapy CrawlSpider中的follow = True

让我们来看看这些规则是如何运作的:

def _requests_to_follow(self, response):
    seen = set()
    for n, rule in enumerate(self._rules):
        links = [lnk for lnk in rule.link_extractor.extract_links(response)
                 if lnk not in seen]
        for link in links:
            seen.add(link)
            r = Request(url=link.url, callback=self._response_downloaded)
            yield r

如您所见,当我们关注链接时,响应中的链接将使用for循环通过所有规则提取,然后将它们添加到set对象.

并且所有响应将由以下方式处理self._response_downloaded:

def _response_downloaded(self, response):
    rule = self._rules[response.meta['rule']]
    return self._parse_response(response, rule.callback, rule.cb_kwargs, rule.follow)

def _parse_response(self, response, callback, cb_kwargs, follow=True):

    if callback:
        cb_res = callback(response, **cb_kwargs) or ()
        cb_res = self.process_results(response, cb_res)
        for requests_or_item in iterate_spider_output(cb_res):
            yield requests_or_item

    # follow will go back to the rules again
    if follow and self._follow_links:
        for request_or_item in self._requests_to_follow(response):
            yield request_or_item

它self._requests_to_follow(response)又一次又一次地回到了原点.

综上所述: