the Gridder class should be an abstract class about xrayutilities

[dkriegner]

there is a similar issue with LayerModel, Material and DarwinModelAlloy which are not usable themselves, but serve as a useful abstraction for derived classes

[eugenwintersberger]

Hi Dominik. If I understood that correctly there is no way to render a class pure abstract in Python as long as you want to support both, Python 2.7 and Python 3.X. In Python 3.X ABC would be the right way to go.

[dkriegner]

I will investigate to which level the abc is usable in python 2.7. I think the goal of this is not to make this 100% clean from programming point of view, but to deliver a reasonable error message to the user when he wants to initialize one of these classes which are not fully functional...

[dkriegner]

@eugenwintersberger could you comment on the mentioned commit? from my point of view thats a viable solution for this issue. if you agree i will put a similar code into the other mentioned classes.

the python2 & 3 compatible code was taken from https://stackoverflow.com/questions/35673474/using-abc-abcmeta-in-a-way-it-is-compatible-both-with-python-2-7-and-python-3-5

[dkriegner]

I consider this issue solved for the moment. Once only python3.3+ is considered as target version one could make improvements and use new functionality of the abc module.