[rbonvall]

I'm also a FP fanboy, and this concept doesn't quite convince me. I'm not sure a Maybe type really helps that much in a dynamically typed language. All the safety you get from using Maybes is worth Nothing (pun intended) when credit_amount could still return let's say Just a string, or raises an exception.

If this chain of calls supposedly handles Nones at any level, then .map is not the right method. It should be .flatMap (or .bind). Unless this is a magic .map that handles either X or Maybe[X] and even exceptions (just like JS promises). This flexibility may be convenient and I can appreciate its pythonicness, but it's not really in the spirit of typed FP.