Custom Lenient URL Regex

I need a very very lenient URL regular expression that works with Python's re module. Before you say it, I have Googled and tried many of the ones available on the web.

Writing a robust regular expression like this myself would be way beyond my current abilities.

If you Google for "improved_regex_for_matching_urls" you will find the most popular one, it has a couple of flaws:
* It cannot cope with subdomains
* It will match www . google . com (Ignore spaces added due to new user forum rule block.) fine but not google.com

Perhaps someone could modify the above one or write another one from scratch. I believe other people might find this solution useful, perhaps for making a wiki/CMS.

I avoid writing complicated regular expressions, preferring instead a divide-to-conquer approach.
Another good thing to avoid---the ill-defined problem.

Perhaps you could write in Backus-Naur form what you consider a valid address?

Perhaps you could use the popular regular expression, and if it fails prepend www. , try again.

I remembered that I have a old friend that uses regexes, and he wrote me this wonderful little one: