Twisted
抓网页，它有优秀的非同步事件驱动的架构，常见的协定都已经有实做，包括HTTP、SMTP等等
getPage("http://www.google.com").addCallback(printPage)
一行就可以抓网页
lxml
效率高，支持xpath
def getNextPageLink(self, tree):
"""Get next page link
@param tree: tree to get link
@return: Return url of next page, if there is no next page, return None
"""
paging = tree.xpath("//span[@class='paging']")
if paging:
links = paging[0].xpath("./a[(text(), '%s')]" % self.localText['next'])
if links:
return str(links[0].get('href'))
return None
listPrice = tree.xpath("//*[@class='priceBlockLabel']/following-sibling::*")
if listPrice:
detail['listPrice'] = self.stripMoney(listPrice[0].text)
使用的工具
FireFox的插件，XPath checker等xpath的工具，可以先用它来确定抓到的元素是正确的，然后FireBug在检视网页结构
