But I think frameworks are not that important. I use Flask mostly for its HTTP request handling functionality. But everything else is my own (e.g., the overall setup, configuration etc).
I think what's most important is understanding that loosely coupled components are the way to go. Know how your scripting language loads and manages modules and try to get to a simple convention on how to organize your code. Minimize the use of ready-to-use extensions and just try to effing know. how. things. work. Glue code together yourself. Document religiously how you did it[1]. It'll save you a world of trouble.
The one tool that has been central to my web development work in Python is pretty much framework-agnostic: Fabric. My projects start with a single fabfile.py and and lib/ directory. I do most of the prototyping in the fabfile.py, which serves as a sort of adhoc testing sandbox[2]. And then I start adding request handlers and writing markup/css. With this approach, whether you're using Flask, webpy or Juno (my faves) is irrelevant. But sticking with Flask might give you a more enthusiastic and active community nowadays.
[1] http://tom.preston-werner.com/2010/08/23/readme-driven-devel...