Selecting the correct settings file to use in Django

Question

I'm following the approach in Two Scoops of Django: Best Practices for Django 1.6 regarding multiple settings files. I'm using Django 1.7 and virtualenvwrapper.

My setup is as follows:

project/
    app1/
    app2/
    project/
        __init__.py
        settings/
            __init__.py
            base.py
            local.py
            production.py
    manage.py

I'm a bit confused as to how Django knows which settings file to use. I do not want to specify the settings file every time I run manage.py. I would rather like to set the DJANG_SETTINGS_MODULE environmental variable as explained in omouse anser here:

What confuses me is in the wsgi.py file there is a line:

os.environ.setdefault("DJANGO_SETTINGS_MODULE", "{{ project_name }}.settings.production")

Is this file only used in the production server? What happens if I already have a DJANGO_SETTINGS_MODULE environmental variable defined on the server?

When running it locally, I understand I need to set the DJANGO_SETTINGS_MODULE env variable every time I open the console. I've read here that I can define a postactivate hook in virtualenvwrapper. This hook will then create the environmental variables that I require everytime I activate the environment.

Is this the recommended way of ensuring the correct DJANGO_SETTINGS_MODULE env variable is loaded on my local machine? Would I also need to setup a similar file on my hosting server? I'm planning on using PythonAnywhere for hosting.

Lastly, if I run a staging server, how would I tell Django to load the staging settings file? The staging server is the practically the same as the production server, so I guess need a different wsgi.py file for the staging server, but that seems like a anti-pattern.

Answer 1

os.environ.setdefault only sets the value if it is not set. When you run in production, export the environment variable DJANGO_SETTINGS_MODULE and set it to your production/staging settings file, and you don't have to set anything when running in development (if you set it by default to your development settings). This is the DRY-est method.

The method with a local_settings.py (which is most of the times kept out of the repo!) is not best practice and should be avoided.