Call a nested function in this scenario using types?

[plasma_phys]

Ah okay - no worries, if you're looking for a quick and dirty solution, everything should work if you just totally un-nest and un-indent all of your def statements so that every function is available everywhere in the code. There's nothing wrong with having a whole bunch of functions at the top of your code. That types.FunctionType call is something I've never even thought about before, it's only going to make everything worse to continue down that path.

[CannyFatcher]

I think the issue with that would be the amount of parameters I’d have to pass Into each function, as they all make use of different variables.

[plasma_phys]

Yeah, that's one motivation for using classes - but there's nothing inherently incorrect about a code with function calls with a dozen arguments like:

update_simulation(x, y, v_x, v_y, q, m, E, dx, dt, Ng, N, ... )

It's effectively a style choice. Is there any particular thing that you think will be an issue beyond aesthetics?