I may have finally found the Python-in-a-sandbox solution I've been looking for... here's my latest experiment, this time running MicroPython in WebAssembly inside my Python applications https://simonwillison.net/2026/Jun/6/micropython-in-a-sandbox/
@simon I was curious about Monty as well, I checked out your research post about it. It might add support for classes in the future, but it looks like it's not planning to support third-party libraries which would restrict plug-in development.