Unless the end user is not technical, use a .py file and force them to subclass your Configuration class which has an __init_subclass__ method so you can enforc

Unless the end user is not technical, use a .py file and force them to subclass your Configuration class which has an __init_subclass__ method so you can enforce rules. When you are ready to move to a more generic solution, your .config or .yml file can generate these. The advantage here is both flexibility (it's Python) and control (allow/disallow whatever you want). If you need nested items, use nested classes.