How to properly close a process in python?

Question

Python

A program with 3-5 processes, when closing and restarting processes, starts to behave strangely, for example, if the code has changed and you need to use the updated one, it turns out to be the devil ...
Whether the functions begin to be duplicated, then they are not executed correctly.
At the same time, when the execution is duplicated, I did not observe additional running processes, it was just that the process tried to perform the entire action x2.

I heard about zombie processes that remain and can be re-called when a similar function is run, but I don’t know much about it.
As a rule, I tried to kill processes with the process.kill() command.
How to kill a process completely? So that after completion and re-launch, it doesn’t freak out.