There is a difference between python runtime and python applications. Also, from the point of view of the PyS60 application developer, this is more than interesting ...
Version 1.9.5 comes by default with memory sizes up to 100k min and 4M max. Of course, you can define them yourself when creating the SIS package for the release and distribution of your application.
Sorry if I answered the right question with the wrong answer (stack against heap).
"", . - :) . , , esp .