Hi<p>The python code that&#x27;s generated is ok, but the problem is that everything is very dynamic. If you want this to work fast on PyPy, it should really generate a bunch of getters and setters that use attribute access and not go through generic __getattr__ that does some dictionary lookups. Additionally a lot of code is written in a way that creates a lot of temporary lists iterating over all fields and double checking stuff - this is bound to be way slower than a simple C&#x2F;Java stuff that does the very simplest &quot;check type - attribute access&quot; sort of stuff.