Django: Concurrent access to settings.py
as e4c5 mentioned, conventionally settings.py is pretty light on logic.  The loading mechanism for settings is pretty obscure and, I personally, like to stay away from things that are difficult to understand and interact with :)
You absolutely have to care about concurrency.  How are you running your application?  It's tricky because in the dev env you have a simple server and usually handle only a handful of requests at the same time (and a couple years ago the dev server was single threaded)
If you're running your application using a forking server, how will you share data between processes? one process won't even see the other processes settings.py changes.  I'm not even sure of how it would look like with a threading server, but it would probably at least require a source code audit of your web server to understand the specifics of how requests are handled and how memory is shared.
Using a DB is by far the easiest solution, (you should be able to use an in memory db as an option too memcache/redis/etc).  DB's provide concurrency support out the box and will be a lot more easier to reason about and provides primitives for concurrent accessing of data.  And in the case of redis, which is single threaded you won't even have to worry about concurrent accesses to your shared IP addresses
I am not sure whether I have to care about concurrency, but I didn't find any documentation about it. 
I have some data stored at my settings.py like ip addresses and each user can take one or give one back. So I have read and write operations and I want that only one user read the file at the same moment.
How could I handle this? 
And yes, I want to store the data at the settings.py. I found also the module django-concurrency. But I couldn't find anything at the documentation.