preferences file

[Dave]

I'm doing a small application and want to add user preferences.  Did 
some googling to see if there are standard Python ways/tools, but it 
seems not so much.  My specific questions are:

1. Best practices for a user preference file/system?

2. File format favored and why - ini, JSON, etc?

3. File location?  I'm using Ubuntu and I believe that the correct 
location would be home/.config/<app-name> .  What about Mac and Windows?

Would like to find a Python library that handles all of this, but so far...

Thanks,
Dave