[m_mueller]

Regarding the GIL I‘ve always wondered about Jython but never gotten around to trying it. What are the drawbacks of running it on a JVM to get true multithreading? Having to properly sync the threads like in other environments without global locks?

[pas]

Nothing, it's just not maintained. People realized, that yeah, python is nice, but why spend years reimplementing it on the JVM, when there's Kotlin. (And Java itself is quite a breeze to program in nowadays. And of course Scala, if you dare go beyond the Pythonic simplicity.)

[yorwba]

Jython doesn't look completely unmaintained: https://hg.python.org/jython

It's also not completely obsoleted by Kotlin, e.g. for the use case of calling a Python library from Java. However, the Python semantics are not a great fit for the JVM, so you should expect it to be slower than plain CPython: https://pybenchmarks.org/u64q/jython.php