Jython isn't (yet) implemented on Truffle, I believe (and would require basically a rewrite).

The approach chrisseaton describes is generally only feasible if you're implementing a Futamura projection à la PyPy or Truffle.

That said, it's only a matter of time before a high-performance Python pops up on Truffle and JITs extensions like RubyTruffle.

There is however ZipPy which is a Py3 implementation built on Truffle, though obviously not directly comparable to the Py2 Jython.