It's all based on BeakerX which has autotranslation b/w languages as one of its key features. I believe it currently it is based on Py4J which does require cop

It's all based on BeakerX which has autotranslation b/w languages as one of its key features. I believe it currently it is based on Py4J which does require copying of the data but I think not expensive serialization, so its reasonably efficient, at least, enough so that it works for plotting. However the discussion is around moving everything to Apache Arrow which in theory supports in-memory shared data b/w languages. Whether that will ever happen is a question though ... the issue has been open for 1.5 years without visible signs of activity. I stopped bothering with autotranslation in the end because I found BeakerX native plots (which work natively from all the languages it supports) actually nicer and more intuitive than Matplotlib. I use it extensively with Groovy.