Interestingly, and possibly confusingly, there's a different project called Beaker Notebook which is polyglot Jupyter notebooks that let you switch back and for

Interestingly, and possibly confusingly, there's a different project called Beaker Notebook which is polyglot Jupyter notebooks that let you switch back and forth between different languages, R, Julia, Python, Scala, and they all share data, write one cell in python and the next in Julia, and then send jobs to Spark clusters. (http://beakernotebook.com/ http://beakernotebook.com/)