Scrapy 抓取：已抓取 0 页

Question

我正在创建一个简单的 scrapy 项目以更好地了解如何使用它，我打算做的是抓取 StackOverflow 的问题页面。

我的蜘蛛被称为first，这是文件的内容。

# -*- coding: utf-8 -*-
import scrapy
from scrapy.spiders import CrawlSpider, Rule
from scrapy.linkextractors import LinkExtractor


class FirstSpider(CrawlSpider):
    name = 'first'
    allowed_domains = ['stackoverflow.com']
    start_urls = ['https://stackoverflow.com/questions']

    rules = (
            Rule(LinkExtractor(allow=['/questions/\?page=\d&sort=newest']), callback='parse_item', follow=True),
    )

    def parse_item(self, response):
        item = scrapy.Item()

        selector_list = response.css('.question-summary')

        for selector in selector_list:
            item['question'] = selector.css('h3 a::text').extract()
            item['votes'] = selector.css('.vote-count-post strong::text').extract()
            item['answers'] = selector.css('.status strong::text').extract()
            item['views'] = selector.css('.views::text').extract()
            item['username'] = selector.css('.user-details a::text').extract()
            item['user-link'] = selector.css('.user-details a::attr(href)').extract()

        return item

然后它应该遍历收集信息的问题页面。

我可以从 shell 获取数据，但是当我尝试抓取或保存输出时失败。

这是scrapy crawl first的输出：

2018-04-07 13:57:06 [scrapy.utils.log] INFO: Scrapy 1.5.0 started (bot: scraper)
2018-04-07 13:57:06 [scrapy.utils.log] INFO: Versions: lxml 4.2.1.0, libxml2 2.9                                                               .5, cssselect 1.0.3, parsel 1.4.0, w3lib 1.19.0, Twisted 17.9.0, Python 2.7.14 (                                                               v2.7.14:84471935ed, Sep 16 2017, 20:19:30) [MSC v.1500 32 bit (Intel)], pyOpenSS                                                               L 17.5.0 (OpenSSL 1.1.0h  27 Mar 2018), cryptography 2.2.2, Platform Windows-XP-                                                               5.1.2600-SP3
2018-04-07 13:57:06 [scrapy.crawler] INFO: Overridden settings: {'NEWSPIDER_MODU                                                               LE': 'scraper.spiders', 'SPIDER_MODULES': ['scraper.spiders'], 'ROBOTSTXT_OBEY':                                                                True, 'BOT_NAME': 'scraper'}
2018-04-07 13:57:06 [scrapy.middleware] INFO: Enabled extensions:
['scrapy.extensions.logstats.LogStats',
 'scrapy.extensions.telnet.TelnetConsole',
 'scrapy.extensions.corestats.CoreStats']
2018-04-07 13:57:07 [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.httpproxy.HttpProxyMiddleware',
 'scrapy.downloadermiddlewares.stats.DownloaderStats']
2018-04-07 13:57:07 [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']
2018-04-07 13:57:07 [scrapy.middleware] INFO: Enabled item pipelines:
[]
2018-04-07 13:57:07 [scrapy.core.engine] INFO: Spider opened
2018-04-07 13:57:07 [scrapy.extensions.logstats] INFO: Crawled 0 pages (at 0 pag                                                               es/min), scraped 0 items (at 0 items/min)
2018-04-07 13:57:07 [scrapy.extensions.telnet] DEBUG: Telnet console listening o                                                               n 127.0.0.1:6023
2018-04-07 13:57:08 [scrapy.core.engine] DEBUG: Crawled (200) <GET https://stackoverflow.com/robots.txt> (referer: None)
2018-04-07 13:57:09 [scrapy.core.engine] DEBUG: Crawled (200) <GET https://stackoverflow.com/questions> (referer: None)
2018-04-07 13:57:09 [scrapy.core.engine] INFO: Closing spider (finished)
2018-04-07 13:57:09 [scrapy.statscollectors] INFO: Dumping Scrapy stats:
{'downloader/request_bytes': 502,
 'downloader/request_count': 2,
 'downloader/request_method_count/GET': 2,
 'downloader/response_bytes': 35092,
 'downloader/response_count': 2,
 'downloader/response_status_count/200': 2,
 'finish_reason': 'finished',
 'finish_time': datetime.datetime(2018, 4, 7, 10, 57, 9, 609000),
 'log_count/DEBUG': 3,
 'log_count/INFO': 7,
 'response_received_count': 2,
 'scheduler/dequeued': 1,
 'scheduler/dequeued/memory': 1,
 'scheduler/enqueued': 1,
 'scheduler/enqueued/memory': 1,
 'start_time': datetime.datetime(2018, 4, 7, 10, 57, 7, 625000)}
2018-04-07 13:57:09 [scrapy.core.engine] INFO: Spider closed (finished)

Answer 1

项目字段应在items.py 中定义，如此处所述（否则将有KeyError）：https://doc.scrapy.org/en/latest/topics/items.html#declaring-items。

在您的情况下，需要在循环内（而不是在外部）创建和生成上述项目。喜欢：

for selector in selector_list:
    item = QuestionItem()
    item['question'] = selector.css('h3 a::text').get()
    ...
    yield item

另外，考虑使用项目加载器来填充项目：https://doc.scrapy.org/en/latest/topics/loaders.html