I have a question to the AUTH_USER_MODEL in Django:
https://docs.djangoproject.com/en/dev/ref/settings/#auth-user-model
The default value is auth.User. However, the actual model is in auth.models.User. How does Django find the correct class?
I am asking because when I usually use models in Django, I have to write from myapp.models import MyModel. So, why do I not need models in auth.User for AUTH_USER_MODEL?
Can some explain me that or show the code that uses it?
Well you define models in the models.py file of an app. So that means that the module in which you stored the model class is app.models. Therefore the import reads:
from app.models import MyModel
Django has in essence nothing to do with this: this is how Python loads modules and classes from these module(s).
Django however loads - when you for example run the server - the apps that are located in the INSTALLED_APPS list of the settings file (usually settings.py), and thus constructs a "register" where it stores Django models, and it names them in a uniform way: app_name.ModelName. There is no reason to specify models here, since models are defined in models.py, and it thus would only introduce "noise".
You can obtain a reference to the model class with apps.get_model [Django-doc]
from django.apps import apps
apps.get_model('app_name', 'ModelName')It thus then checks the registers of the loaded models, and returns a reference to the model.
Linking through a string is useful (and sometimes required) when there is cyclic referencing. For example if you have two models A and B, and A refers to BandBthroughA(for example withForeignKeys), then one of the two models is defined first. This means that if you defineAfirst, it can not refer to theB` class itself, since at that point it does not yet exists. In Django, one then specifies the model through a string. The Django system will then first load the models, and then "tie the knot": resolve the references by replacing the strings with a reference to the actual model class.