How is it more convenient and correct to make your edits to an open project (git) in python without affecting the project itself?

Question

Python

Hello everybody!
There is an open python project that the community is sawing. git repository.
It is necessary to add, and sometimes change the behavior of the program, for example:
1) add a button to the panel
2) in the function that saves the file, add another message output
3) somewhere almost completely replace the module
These changes are purely for your tasks, and are not needed for the main project .
Attention question:
1) how to implement adding and replacing modules and/or only functions or only part of a function in python ?
2) how to track changes in the main git project?
And most importantly, how to do it without pain?)
Now I did it as follows:
1) my git project has two remotes: on the main one and on my repository
2) next to the project there is a folder with my files
3) I launch the main project from my file:

from base_project import *

class main_project_Launcher(base_project_Launcher):

    def __init__(self):
        base_project_Launcher.__init__(self)

if __name__ == '__main__':
    base_project = main_project_Launcher()
    base_project.Start()

The project is being actively sawn, and I would like to constantly update it.
update: the question is more about python than git.

Answer 1

Fork and permanent pools with merging.