python - XPath 不指向正确的 HTML 表格元素与迭代器 (Scrapy)

Question

我在使用 XPath 从表中通过 Scrapy 选择 HTML 元素时遇到问题。我使用的示例是来自 Scrapy 网站的非常基本的示例:http://doc.scrapy.org/en/latest/intro/tutorial.html我要解析的网站是 http://www.euroleague.net/main/results/showgame?gamecode=5&gamenumber=1&phasetypecode=RS&seasoncode=E2013#!playbyplay

一开始我用的是这段代码:

from basketbase.items import BasketbaseItem
from scrapy.contrib.spiders import CrawlSpider, Rule
from scrapy.contrib.linkextractors.sgml import SgmlLinkExtractor
from scrapy.selector import HtmlXPathSelector
from scrapy.http import HtmlResponse


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

    allowed_domains = ["www.euroleague.net"]
    start_urls = ["http://www.euroleague.net/main/results/showgame?gamenumber=1&phasetypecode=RS&gamecode=4&seasoncode=E2013"]
    rules = (
        Rule(SgmlLinkExtractor(allow=(),),callback='parse_item',),        
    )  


    def parse(self,response):
        response = HtmlResponse(url=response.url, status=response.status, headers=response.headers, body=response.body)
        return super(Basketspider,self).parse(response)

    def parse_item(self, response):
        response = HtmlResponse(url=response.url, status=response.status, headers=response.headers, body=response.body)
        sel = HtmlXPathSelector(response)

        items=[]
        item = BasketbaseItem()         
        item['game_time'] = sel.select('//div[@style="overflow: auto; height: 250px; width: 800px;"]/table/tbody/tr/td[1]/text()').extract() #
        item['game_event'] = sel.select('//div[@style="overflow: auto; height: 250px; width: 800px;"]/table/tbody/tr/td[2]/text()').extract() #
        item['game_event_res_home'] = sel.select('//div[@style="overflow: auto; height: 250px; width: 800px;"]/table/tbody/tr/td[3]/text()').extract() #
        item['game_event_res_visitor'] = sel.select('//div[@style="overflow: auto; height: 250px; width: 800px;"]/table/tbody/tr/td[3]/text()').extract() #
        item['game_event_team'] = sel.select('//div[@style="overflow: auto; height: 250px; width: 800px;"]/table/tbody/tr/td[4]/text()').extract() #
        item['game_event_player'] = sel.select('//div[@style="overflow: auto; height: 250px; width: 800px;"]/table/tbody/tr/td[5]/text()').extract() #          
        items.append(item)



        return items

嗯，这是基本的，目前规则不是很正确，但这个例子的主要问题是 XPath。

它可以工作，但不是我想要的方式。我希望每个项目只提取每个 tr 的一个 td 值，但使用此代码，它会立即将所有 td 元素提取到项目中。项目 game_event_res_visitor:

'game_event_res_visitor': [u'0-0',
                           u'0-0',
                           u'0-0',.......(list goes on and on)

为了得到我想要的结果，我决定使用循环(就像在 Scrapy 教程中一样(http://doc.scrapy.org/en/latest/intro/tutorial.html))，但它根本不返回任何值。这是代码:

def parse(self,response):
    response = HtmlResponse(url=response.url, status=response.status, headers=response.headers, body=response.body)
    return super(Basketspider,self).parse(response)

def parse_item(self, response):
    response = HtmlResponse(url=response.url, status=response.status, headers=response.headers, body=response.body)
    sel = HtmlXPathSelector(response)
    sites = sel.xpath('//div[@style="overflow: auto; height: 250px; width: 800px;"]/table/tbody/tr')        
    items=[]
    item = BasketbaseItem()
    for site in sites:

        item = BasketbaseItem()
        item['game_time'] = sel.select('td[1]/text()').extract() #
        item['game_event'] = sel.select('td[2]/text()').extract() #
        item['game_event_res_home'] = sel.select('td[3]/text()').extract() #
        item['game_event_res_visitor'] = sel.select('td[3]/text()').extract() #
        item['game_event_team'] = sel.select('td[4]/text()').extract() #
        item['game_event_player'] = sel.select('td[5]/text()').extract() #          
        items.append(item)



    return items

和终端输出:

2014-03-07 16:57:45+0200 [playbyplay] DEBUG: Scraped from <200 http://www.euroleague.net/main/results/showgame?gamecode=9&gamenumber=1&phasetypecode=RS&seasoncode=E2013>
    {'game_event': [],
     'game_event_player': [],
     'game_event_res_home': [],
     'game_event_res_visitor': [],
     'game_event_team': [],
     'game_time': []}
2014-03-07 16:57:45+0200 [playbyplay] DEBUG: Scraped from <200 http://www.euroleague.net/main/results/showgame?gamecode=9&gamenumber=1&phasetypecode=RS&seasoncode=E2013>
    {'game_event': [],
     'game_event_player': [],
     'game_event_res_home': [],
     'game_event_res_visitor': [],
     'game_event_team': [],
     'game_time': []}

我知道我的 XPath 有问题，但我不明白是什么。如果我在项目元素中使用相对 XPath，它会给出与第一个示例相同的结果。所以它就在那里，但我无法用我拥有的代码访问它。我什至尝试过“通配符”。

    item['game_time'] = sel.select('*/text()').extract() #
    item['game_event'] = sel.select('*/text()').extract() #
    item['game_event_res_home'] = sel.select('*/text()').extract() #
    item['game_event_res_visitor'] = sel.select('*/text()').extract() #
    item['game_event_team'] = sel.select('*/text()').extract() #
    item['game_event_player'] = sel.select('*/text()').extract() #  

它没有得到任何文本结果。

2014-03-07 19:11:14+0200 [playbyplay] DEBUG: Scraped from <200 http://www.euroleague.net/main/results/showgame?gamecode=7&gamenumber=1&phasetypecode=RS&seasoncode=E2013>
    {'game_event': [u' \r\n', u'\r\n'],
     'game_event_player': [u' \r\n', u'\r\n'],
     'game_event_res_home': [u' \r\n', u'\r\n'],
     'game_event_res_visitor': [u' \r\n', u'\r\n'],
     'game_event_team': [u' \r\n', u'\r\n'],
     'game_time': [u' \r\n', u'\r\n']}

我很困惑，我不明白我的 XPath 或我的代码有什么问题。

Answer 1

这是对我有用的:

def parse_item(self, response):
    response = HtmlResponse(url=response.url, status=response.status, headers=response.headers, body=response.body)
    sel = HtmlXPathSelector(response)

    rows = sel.select('//div[@style="overflow: auto; height: 250px; width: 800px;"]/table/tbody/tr')
    for row in rows:
        item = BasketbaseItem()
        item['game_time'] = row.select("td[1]/text()").extract()[0]
        item['game_event'] = row.select("td[2]/text()").extract()[0]
        result = row.select("td[3]/text()").extract()[0]
        item['game_event_res_home'], item['game_event_res_visitor'] = result.split('-')
        item['game_event_team'] = row.select("td[4]/text()").extract()[0]
        item['game_event_player'] = row.select("td[5]/text()").extract()[0]
        yield item

这是我得到的示例项目:

{'game_event': u'Steal',
 'game_event_player': u'DJEDOVIC, NIHAD',
 'game_event_res_home': u'0 ',
 'game_event_res_visitor': u' 0',
 'game_event_team': u'FC Bayern Munich',
 'game_time': u'2'}

对您来说，这只是一个开始 - 有时项目不会由于 IndexError 异常而产生 - 正确处理它。

希望对您有所帮助。