XPath tips from the web scraping trenches(blog.scrapinghub.com)

40 pointsby predius12 yıl önce5 comments

blog.scrapinghub.com

XPath tips from the web scraping trenches

http://blog.scrapinghub.com/2014/07/17/xpath-tips-from-the-web-scraping-trenches/

2 comments

patrickg12 yıl önce

There are some things in XPath that I really like. For example `x = ( a, b, c )' means: `(x == a or x == b or x == c)' which is quite handy sometimes. Also `(a,default)[1]' makes it easy to provide a default if a is null.

eliasdorneles12 yıl önce

Thanks, that is novelty to me! I don't seem to get an example working, though. Is that XPath 2.0?

patrickg12 yıl önce

Yes, this is XPath 2.0. I don't bother with 1.0 if I can, because it is soooo far behind 2.0.

data: <data attr="1" />

xsl:

    <?xml version="1.0" encoding="UTF-8"?>
    <xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns:xs="http://www.w3.org/2001/XMLSchema" exclude-result-prefixes="xs" version="2.0">

      <xsl:template match="/data">
        <one>
          <xsl:value-of select="@attr = (2,3,4)" />
        </one>
        <two>
          <xsl:value-of select="(@doesntexist,2)[1]" />
        </two>
      </xsl:template>
    </xsl:stylesheet>

gives: <one>false</one><two>2</two>

eliasdorneles12 yıl önce

That is very cool, indeed! =) I'm stuck with XPath 1.0 still, because XPath 2.0 hasn't found its way to lxml yet -- it seems to be quite a lot of work to implement it.

krapp12 yıl önce

I've been working on a web scraper that uses xpath for a while as part of several projects - resources like this are very much appreciated.