I realize you think the problem is that I don't understand what docstrings are, but it's more that you don't understand the sorts of documentation I'm talking about. docstrings are fine for a certain type of limited documentation that is formatted to prevent syntax errors. But they are extremely limited. Reading docstring/doxygen style documentation is the slowest and most error prone in my experience. Particularly when you are describing a complex calculation.

> If your logic is broken up across cells then you cannot use it anywhere but in that notebook...

You don't seem to understand how notebooks can be used and processed themselves. They are just data and there are libraries for loading and transforming them. You might check out pydev and papermill to get an idea about this (and maybe also literate programming in general).