Guideline for attributes

[TeresiaOlsson]

When going through the code I found different ways of how attributes are implemented and I also wasn't entirely sure what to go for myself when doing changes. So I thought deciding on a guideline would be good.

This is my suggestion:

• For attributes that are meant to be public to users or other classes and where no special logic is needed for getting/settings, use regular attributes, e.g. self.x.

• For attributes that are intended to be private to a class and never called by another class use single underscore, e.g. self._x.'
  If another class calls such an attribute, it means the implementation is wrong and should be modified.

• For attributes that need special logic for getting/setting, use single underscore + property decorator for getter/setter. Only make functions like get_something and set_something if there is a specific use case for it.

• Never use double underscore unless you have a specific use case where it is necessary. This is because name mangling make the code more difficult to understand and debug for non-expert Python programmers.

[gubaidulinvadim]

I think your suggestion is alright. I only slightly disagree on get and set. I don't mind so much having get/set functions instead of properties, even if it is not so Pythonic. Maybe the guidelines should be added to CONTRIBUTING.md or to some other visible place.

[TeresiaOlsson]

I think get/set functions are okay if there is a valid reason for it but since it's not the Pythonic way it's not a good idea to overuse it. Better for the future to embrace the philosophy of the chosen language since it makes the code easier to understand for new users and developers.

[TeresiaOlsson]

I also discovered now that using properties makes it easier to implement a generic __repr__ function which automatically prints all the attributes that are meant to be public for the users. So far we have relied on there being a ConfigModel where you can get those attributes for the __repr__ but if we decide to not enforce config models for all classes to make things more flexible we need some other option to automatically generate the __repr__ or we have to implement it on each class which is annoying.