Xpath 使用 Scrapy 在下一个兄弟标签中获取信息

Posted 2023-02-23

【中文标题】Xpath 使用 Scrapy 在下一个兄弟标签中获取信息

【英文标题】：Xpath to get information in next sibling tag using Scrapy

【发布时间】：2015-01-24 04:48:50

【问题描述】：

我正在尝试使用 Scrapy，现在我尝试从一个词源网站中提取信息：http://www.etymonline.com 现在，我只想获取单词及其原始描述。这就是通常的 html 代码块在 etymonline 中的呈现方式：

<dt>
  <a href="/index.php?term=address&allowed_in_frame=0">address (n.)</a>
  <a href="http://dictionary.reference.com/search?q=address" class="dictionary" title="Look up address at Dictionary.com">
    <img src="graphics/dictionary.gif"    title="Look up address at Dictionary.com"/>
  </a>
</dt>
<dd>
  1530s, "dutiful or courteous approach," from <a href="/index.php?term=address&allowed_in_frame=0" class="cros-s-reference">address</a> (v.) and from French <span class="foreign">adresse</span>. Sense of "formal speech" is from 1751. Sense of "superscription of a letter" is from 1712 and led to the meaning "place of residence" (1888).
</dd>

这个词包含在<dt>标签和下一个兄弟<dd>标签中的描述。 要获取像http://www.etymonline.com/index.php?l=a&p=9&allowed_in_frame=0 这样的页面上的单词列表，可以写成word = sel.xpath('//dl/dt/a/text()').extract()。

然后我尝试遍历这个单词列表并使用这行代码info = selInfo.xpath("//dl/dt[a='"+word[i]+"']/following-sibling::dd")提取相关信息。但这似乎不起作用。有什么想法吗？

【问题讨论】：

你有word[i] 中<a> 元素的完整 内容吗（例如：“address (n.)”，而不是“address”？否则，您可能想使用starts-with。

【参考方案1】：

使用跟随兄弟的解决方案。

class SingleSpider(scrapy.Spider):
    name = "etym"
    allowed_domains = ["etymonline.com"]
    start_urls = [
        "http://www.etymonline.com/index.php?l=d&allowed_in_frame=0"]

    def parse(self, response):


        for nodes in response.xpath('//dl'):
            for i in nodes.xpath('dt'):
                print i.xpath('a/text()').extract()   
                print i.xpath('following-sibling::dd[1]/text()').extract()    

基本上：

你一个一个得到Dt元素 打印链接中包含的文本 移动到下一个兄弟并打印包含的文本 列表项

这里是输出的摘录：

[u'daiquiri (n.)'] [u'类型的酒精饮料，1920 年（首次记录于 F. Scott Fitzgerald), 来自 ', u', 地区或村庄的名称 古巴东部。']

[u'dairy (n.)'] [u'late 13c., “用于制作黄油和奶酪的建筑； 奶牛场”，由英法 ', u' 组成，加在中古英语上 ', u' (in ', u' "dairymaid"), 源自古英语 ', u' "kneader of 面包、管家、女仆”（见 ', u' (n.1)）。纯粹的 母语是', u'。']

[u'dais (n.)'] [u'mid-13c., 源自盎格鲁-法语', u', 古法语', u' “桌子，平台”源自拉丁语 '，u'，“圆盘状物体”，也由 中世纪时期，“table”，源自希腊语 '，u'，“quoit，disk，dish”（参见 '， 你'（名词））。死于英语 c.1600，保存在苏格兰，复活 19c。由古物学家。']

【参考方案2】：

要在<dt> 之后到达<dd>，您可以使用following-sibling 轴，没错。

following-sibling::dd 选择上下文节点后的所有 dd 元素。因此，您需要使用位置谓词 [1] 将 XPath 限制为仅第一个。

对于您从//dl/dt 得到的每个dt 元素，您选择following-sibling::dd[1]。

这是一个使用scrapy shell 表示“地址”一词的示例会话：

$ scrapy shell "http://www.etymonline.com/index.php?allowed_in_frame=0&search=address&searchmode=none"
...
2014-11-26 10:34:53+0100 [default] DEBUG: Crawled (200) <GET http://www.etymonline.com/index.php?allowed_in_frame=0&search=address&searchmode=none> (referer: None)
[s] Available Scrapy objects:
[s]   crawler    <scrapy.crawler.Crawler object at 0x7f1396cc6950>
[s]   item       
[s]   request    <GET http://www.etymonline.com/index.php?allowed_in_frame=0&search=address&searchmode=none>
[s]   response   <200 http://www.etymonline.com/index.php?allowed_in_frame=0&search=address&searchmode=none>
[s]   settings   <scrapy.settings.Settings object at 0x7f1397399bd0>
[s]   spider     <Spider 'default' at 0x7f13966c05d0>
[s] Useful shortcuts:
[s]   shelp()           Shell help (print this help)
[s]   fetch(req_or_url) Fetch request (or URL) and update local objects
[s]   view(response)    View response in a browser

In [1]: for dt in response.xpath('//dl/dt'):
    print "Word:", dt.xpath('string(a)').extract()
    print "Definition:", dt.xpath('string(following-sibling::dd[1])').extract()
    print
   ...:     
Word: [u'address (n.)']
Definition: [u'1530s, "dutiful or courteous approach," from address (v.) and from French adresse. Sense of "formal speech" is from 1751. Sense of "superscription of a letter" is from 1712 and led to the meaning "place of residence" (1888).']

Word: [u'addressee (n.)']
Definition: [u'1810; see address (v.) + -ee.']

Word: [u'address (v.)']
Definition: [u'early 14c., "to guide or direct," from Old French adrecier "go straight toward; straighten, set right; point, direct" (13c.), from Vulgar Latin *addirectiare "make straight," from Latin ad "to" (see ad-) + *directiare, from Latin directus "straight, direct" (see direct (v.)). Late 14c. as "to set in order, repair, correct." Meaning "to write as a destination on a written message" is from mid-15c. Meaning "to direct spoken words (to someone)" is from late 15c. Related: Addressed; addressing.']

Word: [u'salutatorian (n.)']
Definition: [u'1841, American English, from salutatory "of the nature of a salutation," here in the specific sense "designating the welcoming address given at a college commencement" (1702) + -ian. The address was originally usually in Latin and given by the second-ranking graduating student.']

...

Word: [u'reverend (adj.)']
Definition: [u'early 15c., "worthy of respect," from Middle French reverend, from Latin reverendus "(he who is) to be respected," gerundive of revereri (see reverence). As a form of address for clergymen, it is attested from late 15c.; earlier reverent (late 14c. in this sense). Abbreviation Rev. is attested from 1721, earlier Revd. (1690s). Very Reverend is used of deans, Right Reverend of bishops, Most Reverend of archbishops.']

Word: [u'nun (n.)']
Definition: [u'Old English nunne "nun, vestal, pagan priestess, woman devoted to religious life under vows," from Late Latin nonna "nun, tutor," originally (along with masc. nonnus) a term of address to elderly persons, perhaps from children\'s speech, reminiscent of nana (compare Sanskrit nona, Persian nana "mother," Greek nanna "aunt," Serbo-Croatian nena "mother," Italian nonna, Welsh nain "grandmother;" see nanny).']


In [2]: 

【参考方案3】：

xpath 工作的想法不是loop 提取的列表，而是在 xpath 的父节点内。

目前我的 Mac 上没有 scrapy，但这里的技术应该同样适用，如下所示：

# I use lxml for loose html string parsing
from lxml import html

s = '''<dt><a href="/index.php?term=address&allowed_in_frame=0">address (n.)</a> <a href="http://dictionary.reference.com/search?q=address" class="dictionary" title="Look up address at Dictionary.com"><img src="graphics/dictionary.gif"    title="Look up address at Dictionary.com" /></a></dt>
<dd>1530s, "dutiful or courteous approach," from <a href="/index.php?term=address&allowed_in_frame=0" class="cros-s-reference">address</a> (v.) and from French <span class="foreign">adresse</span>. Sense of "formal speech" is from 1751. Sense of "superscription of a letter" is from 1712 and led to the meaning "place of residence" (1888).</dd>'''

sel = html.fromstring(s)

# rather than extracting the words straight away, you loop from the parent xpath
for nodes in sel.xpath('//dt'):
    # then access a node to get the text
    print nodes.xpath('a/text()')
    # and go back to parent and search the dd node
    print nodes.xpath('../dd/text()')

# sample results
['address (n.)']
['1530s, "dutiful or courteous approach," from ', ' (v.) and from French ', '. Sense of "formal speech" is from 1751. Sense of "superscription of a letter" is from 1712 and led to the meaning "place of residence" (1888).']

希望这会有所帮助。