response.xpath('/html').extract()
[u'<html><head><title>...</body></html>']
response.xpath('/html/body/div/h1').extract()
[u'<h1>Example Domain</h1>']
response.xpath('/html/body/div/p').extract()
[u'<p>This domain… permission.</p>', u'<p><a
href="http://www.iana.org/domains/example">More information…</a></p>']
response.xpath('//html/head/title').extract()
[u'<title>Example Domain</title>']
response.xpath('//a').extract()
[u'<a href="http://www.iana.org/domains/example">More information…</a>']
response.xpath('//a/@href').extract()
[u'http://www.iana.org/domains/example']
response.xpath('//a/text()').extract()
[u'More information…']
response.xpath('//a[starts-with(@href, "http://www.")]').extract()
[u'<a href="http://www.iana.org/domains/example">More information…</a>']