python如何使用BeautifulSoup分析网页信息

python通过BeautifulSoup分析网页信息，这段python代码查找网页上的所有链接，分析所有的span标签，并查找class包含titletext的span的内容

#import the library used to query a website
import urllib2
 
#specify the url you want to query
url = "http://www.75271.com"
 
#Query the website and return the html to the variable 'page'
page = urllib2.urlopen(url)
 
#import the Beautiful soup functions to parse the data returned from the website
from BeautifulSoup import BeautifulSoup
 
#Parse the html in the 'page' variable, and store it in Beautiful Soup format
soup = BeautifulSoup(page)
 
#to print the soup.head is the head tag and soup.head.title is the title tag
print soup.head
print soup.head.title
 
#to print the length of the page, use the len function
print len(page)
 
#create a new variable to store the data you want to find.
tags = soup.findAll('a')
 
#to print all the links
print tags
 
#to get all titles and print the contents of each title
titles = soup.findAll('span', attrs = { 'class' : 'titletext' })
for title in allTitles:
    print title.contents