Regex for links in html text

Question

I hope this question is not a RTFM one. I am trying to write a Python script that extracts links from a standard HTML webpage (the <link href... tags). I have searched the web for matching regexen and found many different patterns. Is there any agreed, standard regex to match links?

Adam

UPDATE: I am actually looking for two different answers:

1. What's the library solution for parsing HTML links. Beautiful Soup seems to be a good solution (thanks, Igal Serban and cletus!)
2. Can a link be defined using a regex?

Answer 1

Regexes with HTML get messy. Just use a DOM parser like Beautiful Soup.

Answer 2

As others have suggested, if real-time-like performance isn't necessary, BeautifulSoup is a good solution:

import urllib2
from BeautifulSoup import BeautifulSoup

html = urllib2.urlopen("http://www.google.com").read()
soup = BeautifulSoup(html)
all_links = soup.findAll("a")

As for the second question, yes, HTML links ought to be well-defined, but the HTML you actually encounter is very unlikely to be standard. The beauty of BeautifulSoup is that it uses browser-like heuristics to try to parse the non-standard, malformed HTML that you are likely to actually come across.

If you are certain to be working on standard XHTML, you can use (much) faster XML parsers like expat.

Regex, for the reasons above (the parser must maintain state, and regex can't do that) will never be a general solution.