I'd recommend the Plone CMS as a starting point into learning Python. You get a full-featured CMS that you can use from day one for lots of common use cases. With Plone, you have an application that you can take apart to see examples of mature Python development processes. You can also learn just the aspects that are useful to you at a given point in time. Plone has a community that is very friendly, mature, and open to newbies. This makes it a lot easier to get your bearings and get help when you need it. It's also welcome community if you're looking to make your first contributions to Open Source.

Personally, Plone was my first experience in programming with Python. In 2003 I was working as an environmental consultant and started experimenting with Zope and Plone to build knowledge management apps for my clients. In 2004, I made the jump to being a Plone developer full-time and have never looked back. I've found it to be an outstanding platform and have landed clients including US federal agencies, EU government ministries, Fortune 500 companies, and major universities.

Since learning Plone, I've worked with a number of other Python frameworks including Twisted, Pyramid, and Django as well as a couple of Rails projects. Much of what I've learned via Plone gave me a good foundation for working with these other tools. Somehow, I always keep coming back to Plone. It's a great platform for secure, large-scale content-intensive sites and the market for skilled developers is very favorable relative to other frameworks.

Previously: http://news.ycombinator.com/item?id=327710

I'd recommend reading the Django source. I use the framework every day and it seems well put together :-)

Mercurial is well-written Python project:

http://selenic.com/hg