Should code boxes show a prompt?

I can't seem to find if this is detailed anywhere. In the shell-novice lesson the code boxes show the `$` prompt ahead of the command to be run, and this pattern is followed also in the MATLAB-novice, and make-novice lessons. In the python and R lessons there is no prompt.

Is there guidance as to which approach should be taken and why (not)? It would make sense to be consistent across lessons, or to document why there is a difference. I can see reasons for and against.