Sadly, Django is still by far the most popular. It's ok, though. You're likely to not hate it intensely. It also has a lot of third party code available, and a fair amount of functionality built-in.

Flask is nicer (and lets you seamlessly use SQLAlchemy, which is so much better than Django's crappy ORM), but also tiny. It's basically just a bit of glue between werkzeug, SQLAlchemy and Jinja2.

Pyramid has more things in it than Flask and also uses SQLAlchemy.

web2py appears both bad and unpopular to me.