[Django]-Django User model, adding function

This is an update of @Lakshman Prasad’s answer. But a full example:

create a file monkey_patching.py in any of your apps::

#app/monkey_patching.py
from django.contrib.auth.models import User 

def get_user_name(self):
    if self.first_name or self.last_name:
        return self.first_name + " " + self.last_name
    return self.username

User.add_to_class("get_user_name",get_user_name)

and import it in app’s __init__.py file. ie::

#app/__init__.py
import monkey_patching

It’s not unusual to substitute user model as it is stated in the docs: https://docs.djangoproject.com/es/1.9/topics/auth/customizing/#substituting-a-custom-user-model, so, having this into account, it is better to get the user model class with the following code:

from django.contrib.auth import get_user_model
UserModel = get_user_model()

Afterwards, you can use this UserModel to add functionality as @Lakshman Prasad suggests: UserModel.add_to_class('get_related_foo_models', get_related_foo_models).

In order to get the code executed only once I prefer to use Django application config classes (https://docs.djangoproject.com/es/1.9/ref/applications/), so a full working example will be:

# myapp/__init__.py
default_app_config = 'myapp.apps.MyAppConfig'

# myapp/apps.py
from django.apps import AppConfig
from django.contrib.auth import get_user_model


class MyAppConfig(AppConfig):
    name = 'myapp'
    verbose_name = 'MyApp'

    def ready(self):
        # Add some functions to user model:
        def custom_function(self):
            # Do whatsoever
            pass

        UserModel = get_user_model()
        UserModel.add_to_class('custom_function', custom_function)

You can use a proxy model to add methods to the User model without changing it class.

from django.contrib.auth import models

class UserProxy(models.User):
    class Meta:
        proxy = True
    
    def get_related_foo_models(self):
        pass

Get an instance of the proxy model in view – models.UserProxy.objects.get(pk=request.user.pk)

To get an instance of the proxy model immediately from the request, you need to create a custom ModelBackend as described in this question – Django – User proxy model from request.

Source https://docs.djangoproject.com/en/4.1/topics/db/models/#proxy-models