I'd just like to comment that, having built a medium to large Flask app over the last year, I would never recommend it as a framework for non-trivial sites.
I don't even want to sum up the amount of time that Django would have solved my problem instantly, but instead I had to pull my hair out dealing with Flask's global variables, circular dependency issues, and general lack of cohesion or standards. I think it's a great micro-framework if you're writing a one-python-file personal site or blog. Anything larger than that and you're going to regret it.
I disagree. Flask's thread locals have never been a problem for me and it's not like you can escape them, most frameworks use them in some form implicitly, for example both Django and Pyramid. The circular dependency in Flask hasn't been a problem either, once I wrapped my head around how to do it properly. Lack of standards I would say is still a bit of a problem, but Blueprints helped. I wouldn't say Django has this one quite figured out either though, and in general I usually have to do some heavy customization when using 3rd party Django apps with their own views and urls.
I don't even want to sum up the amount of time that Django would have solved my problem instantly, but instead I had to pull my hair out dealing with Flask's global variables, circular dependency issues, and general lack of cohesion or standards. I think it's a great micro-framework if you're writing a one-python-file personal site or blog. Anything larger than that and you're going to regret it.