My favorite way to learn about something like metaclasses in python is to go to stackoverflow and search for '[python] metaclasses' then order by votes. Open up a few of the links that look interesting, and you'll get to see some good uses. In this case, you'll also end up with this awesome explanation near the top:

http://stackoverflow.com/questions/100003/what-is-a-metaclas...

In practice, this works for a wide variety of topics.