The xeus-python jupyterlite-kernel
uses pyjs. In particular the event loop for async programming relies on pyjs.
With the following code one can create a xeus-python instance with a custom set of packages available:
pip install jupyterlite
pip install jupyterlite-xeus-python
jupyter lite build --XeusPythonEnv.packages=numpy,matplotlib,ipyleaflet
jupyter lite serve
A nice example for such a xeus-python jupyterlite instance is the ipycanvas demo:
<iframe width="100%" height="860" src="https://ipycanvas.readthedocs.io/en/latest/lite/lab/"> <iframe>