design for continuation based python web appliction framework
Right, continuation is a property of a language and CPython sadly has not continuations.
The workarounds in pure Python are well known : use callbacks / deferers like Twisted and Tornado for example or use 'yield' everywhere to mimic co-routines, like Diesel. But both approaches force you to change the way you design and code your application. Also a continuation can be "replayed" which is how the continuation based frameworks automatically handle the "back" button problem.
Finally, to be exact, in Nagare we are using the pickling of a freezed tasklet to obtain a continuation object.
There are many continuation based framework for java, ruby etc but none in python. Nagare framework somewhat solves the problem but it do not use standard python and uses stackless python to solve continuation problem. 
I was wondering,
what part of standard python constraint to create such continuation web framework in standard python ?
and What are the workaround to it ? and what are standard part in continuation framework architecture ( as model view controller are in MVC ) ?