I have a list of about 20 objects and for each object I return a list of 10 dictionaries.
I am trying to store the list of 10 dictionaries for each object in the list on
Since this was written, the App Engine has pushed out their experimental "ndb" Python database model, which contains in particular the JsonProperty, something that pretty well directly implements what you want.
Now, you need to be running the Python 2.7 version of the App Engine, which is still not quite ready for production, but it all seems pretty stable these days, GvR himself seems to be writing a lot of the code which bodes well for the code quality, and I'm intending to use this in production sometime this year...