小编典典

Scrapy CrawlSpider用于AJAX内容

scrapy

AJAX调用的参数是“页面”,每次单击“更多”按钮时都会增加。例如,一次单击“更多”将加载其他n条文章,并在“更多”按钮的onClick事件中更新page参数,以便下次单击“更多”时,将加载两篇文章的“页面”(假设“页面“ 0”最初已加载,而“页面” 1首次点击已加载)。

对于每个“页面”,我想使用“规则”抓取每篇文章的内容,但是我不知道有多少个“页面”,并且我不想选择任意的m(例如10k)。我似乎无法弄清楚如何进行设置。

从这个问题,Scrapy抓取网址才能,我试图创造潜力的URL网址列表,但我不能确定如何以及在何处解析前一个URL,并确保以后从池中发送一个新的URL包含新闻链接为CrawlSpider。我的规则将响应发送到parse_items回调,在该回调中分析文章内容。

在应用规则并调用parse_items之前,是否有办法观察链接页面的内容(类似于BaseSpider示例),这样我才能知道何时停止爬网?

简化的代码(为清楚起见,我删除了一些正在解析的字段):

class ExampleSite(CrawlSpider):

    name = "so"
    download_delay = 2

    more_pages = True
    current_page = 0

    allowed_domains = ['example.com']

    start_urls = ['http://example.com/account/ajax_headlines_content?type=in_focus_articles&page=0'+
                      '&slugs=tsla&is_symbol_page=true']

    ##could also use
    ##start_urls = ['http://example.com/symbol/tsla']

    ajax_urls = []                                                                                                                                                                                                                                                                                                                                                                                                                          
    for i in range(1,1000):
        ajax_urls.append('http://example.com/account/ajax_headlines_content?type=in_focus_articles&page='+str(i)+
                      '&slugs=tsla&is_symbol_page=true')

    rules = (
             Rule(SgmlLinkExtractor(allow=('/symbol/tsla', ))),
             Rule(SgmlLinkExtractor(allow=('/news-article.*tesla.*', '/article.*tesla.*', )), callback='parse_item')
            )

        ##need something like this??
        ##override parse?
        ## if response.body == 'no results':
            ## self.more_pages = False
            ## ##stop crawler??   
        ## else: 
            ## self.current_page = self.current_page + 1
            ## yield Request(self.ajax_urls[self.current_page], callback=self.parse_start_url)


    def parse_item(self, response):

        self.log("Scraping: %s" % response.url, level=log.INFO)

        hxs = Selector(response)

        item = NewsItem()

        item['url'] = response.url
        item['source'] = 'example'
        item['title'] = hxs.xpath('//title/text()')
        item['date'] = hxs.xpath('//div[@class="article_info_pos"]/span/text()')

        yield item

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2020-04-09

共1个答案

小编典典

在这里,spider可能太有限了。如果你需要大量逻辑,通常最好从Spider继承。

Scrapy提供了CloseSpider异常,当你需要在某些情况下停止解析时,可以引发该异常。你正在爬网的页面返回一条消息“你的库存中没有焦点文章”,当你超过最大页面数时,你可以检查此消息并在发生此消息时停止迭代。

在你的情况下,你可以执行以下操作:

from scrapy.spider import Spider
from scrapy.http import Request
from scrapy.exceptions import CloseSpider

class ExampleSite(Spider):
    name = "so"
    download_delay = 0.1

    more_pages = True
    next_page = 1

    start_urls = ['http://example.com/account/ajax_headlines_content?type=in_focus_articles&page=0'+
                      '&slugs=tsla&is_symbol_page=true']

    allowed_domains = ['example.com']

    def create_ajax_request(self, page_number):
        """
        Helper function to create ajax request for next page.
        """
        ajax_template = 'http://example.com/account/ajax_headlines_content?type=in_focus_articles&page={pagenum}&slugs=tsla&is_symbol_page=true'

        url = ajax_template.format(pagenum=page_number)
        return Request(url, callback=self.parse)

    def parse(self, response):
        """
        Parsing of each page.
        """
        if "There are no Focus articles on your stocks." in response.body:
            self.log("About to close spider", log.WARNING)
            raise CloseSpider(reason="no more pages to parse")


        # there is some content extract links to articles
        sel = Selector(response)
        links_xpath = "//div[@class='symbol_article']/a/@href"
        links = sel.xpath(links_xpath).extract()
        for link in links:
            url = urljoin(response.url, link)
            # follow link to article
            # commented out to see how pagination works
            #yield Request(url, callback=self.parse_item)

        # generate request for next page
        self.next_page += 1
        yield self.create_ajax_request(self.next_page)

    def parse_item(self, response):
        """
        Parsing of each article page.
        """
        self.log("Scraping: %s" % response.url, level=log.INFO)

        hxs = Selector(response)

        item = NewsItem()

        item['url'] = response.url
        item['source'] = 'example'
        item['title'] = hxs.xpath('//title/text()')
        item['date'] = hxs.xpath('//div[@class="article_info_pos"]/span/text()')

        yield item
2020-04-09