For me, a big one is that Bottle.py has zero dependencies; the entirety of the framework, including the template engine, lives inside the single `bottle.py` Python script. That means it's simple to use even without pip or a virtual environment: just pop the bottle.py file in your project, import from it, run `python my_script.py` in your terminal, and you server is up and running.

From my experience with Flask (albeit, this was years ago), it was a bit more complex and ending up with circular dependencies was common.