I'd suggest django, based on my experience.
About a year or so ago, I was looking for a framework, and narrowed my possibilities down to Catalyst (perl), Django (python) and Rails (ruby).
I was a perl guy, so ruled out Catalyst, as I wanted to learn a new language aswell, so Rails and Django was the two I had a look at.
Both had extensive documentation, I didn't know either language (though, I did dabble into python before, but that was mostly bugfixing some GUI apps, where I knew the toolking from another language anyway).
In the end, after playing with each for about a week, I went with Django, because the ORM seemed much friendlier, and I didn't really like how I'd have to install a bunch of gems if I wanted to play with the bleeding edge rails. Gems, which weren't packaged by my distribution..
With Django, however, I could just check it out from SVN, and that was that. Much easier.
While I understand that this is a non-issue for production apps, where one would bundle all the stuff with the application, when I want to play and learn something, I very much prefer that it works with stuff that my distribution has available. Or at least, there's very little extra I need to install.
As for the learning curve: it took me about two hours to start work on the project I wanted to do (with Django, it was a bit longer with Rails), and I didn't know neither the framework, nor the language all that well before that.
