python中的xpath，为什么'/html'就匹配不到

Question

 from lxml.html.soupparser import fromstring
import urllib2  
response = urllib2.urlopen('http://www.haojiazhang123.com')  
html = response.read()
root = fromstring(html)    
desc_list = root.xpath('/html/body/div[1]/div[3]/ul/li[2]/a')
print desc_list

但是，把xpath改成'//div[@class="navi"]/ul/li[2]/a'就匹配到了呢？

Answer 1

html上层还有没有节点。然后就就是你的整个路径正确吗