BeautifulSoup

Beautiful Soup is a Python library for manipulating HTML pages.

Cookbook (Code Examples)

Getting a Soup from a URL

A useful all-purpose way of reading the contents of a webpage.

It does two important things, beyond a simple URL open:

Sets the "user_agent"
Handles redirection

Uses urllib2.Request to set the "user_agent" string -- in this way the request will appear to be coming from a browser (A Linux version of Firefox in the example given below... but this could be changed to whatever). Some sites attempt to block "bots" by rejecting requests if the user-agent (browser) is not recognizied.

The urllib2.urlopen function deals with eventual redirection to a different page location, which is why the function returns both the soup and the "actual" URL. This "realurl" should be used in any subsequent substitution / absolutizing of URLs inside the page as this is where the page actually is.

def opensoup (url):
	"""
	returns (page, actualurl)
	sets user_agent and resolves possible redirection
	realurl maybe different than url in the case of a redirect
	"""	
	request = urllib2.Request(url)
	user_agent = "Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.8.1.14) Gecko/20080418 Ubuntu/7.10 (gutsy) Firefox/2.0.0.14"
	request.add_header("User-Agent", user_agent)
	pagefile=urllib2.urlopen(request)
	soup=BeautifulSoup.BeautifulSoup(pagefile)
	realurl = pagefile.geturl()
	pagefile.close()
	return (soup, realurl)

Replace the contents of a tag

A function to replace the contents of a tag:

import BeautifulSoup
soup = BeautifulSoup.BeautifulSoup("<ul><li>one</li><li>two</li></ul>")

def setcontents (tag, val):
	# remove previous contents
	for c in tag.contents:
		c.extract()
	# insert the new
	tag.insert(0, val)

items = soup.findAll("li")
for item in items:
	setcontents(item, "foo")

print soup.prettify()

Wrap one (existing) tag inside of another (newly created) tag

import BeautifulSoup

def wraptag (tag, wrapper):
	# <tag>contents</tag> ==> <wrapper><tag>contents</tag></wrapper>
	tagIndex = tag.parent.contents.index(tag)
	tag.parent.insert(tagIndex, wrapper)
	wrapper.insert(0, tag)

# TEST CODE
soup = BeautifulSoup.BeautifulSoup("<ul><li>one</li><li>two</li></ul>")
items = soup.findAll("li")
for item in items:	
	div = BeautifulSoup.Tag(soup, "div")
	wraptag(item, div)
print soup.prettify()

Code Questions

When "absolutizing", how to patch url's in stylesheets.