Thank you very much @josevalim for introducing this problem and for taking the time to join us in this thread, that’s very generous of you!
I am also interested in learning how to ease the migration from imperative to functional. The Python solution appears more accessible than the FP variants, but perhaps we could demonstrate that it is not so simple. In this example, I find it surprising that the lesson_counter assignment in the if scope override the parent scopes. This becomes even more surprising when this happens inside a function scope, see: Why am I getting an UnboundLocalError when the variable has a value?. Taking these scoping rules into consideration, then I am not so sure that the Python solution is really more accessible.