Tornado - the best Python web framework
rz.scale-it.pl
this post explains authors opinion why WSGI is not sufficient and present Tornado, which handles ideal web frameworks problems greatly.
rz.scale-it.pl
All three of those are trapped into the paradigm of receiving URLs and routing them to python methods.
Read this: http://www.nagare.org/trac/wiki/NagareDescription
and see how those 3 frameworks fit exactly what Nagare frees you from.