More on the API here: https://github.com/jythontools/jython/blob/master/src/org/python/util/PythonInterpreter.java
- note that is not even a core API for Jython, it just happens to be widely used, including by the launcher that wraps this API and calls itself the jython executable. So we can readily refactor if we have something better, because right now it is also problematic with respect to its lifecycle; what is the mapping to threads; and how it interacts with class loaders and other resources, especially during cleanup.
It would be helpful to coordinate this subinterpreter work; or at least to cc jython-dev on such ideas your might have. Recently there have been some rumblings of consensus that it's about time for Jython to really start work on the 3.x implementation, targeting 3.6. But do be aware we are usually at most 2 to 5 developers, working in our spare time. So everything takes much longer than one would hope. I just hope we can finish 3.6 (or whatever) before Python 4.0 arrives :)
*Excluding certain cases on core types where our bytecode rewriting makes it a true challenge!