Custom user model with AbstractUser in Django - Step-by-Step Execution

Concept Flow - Custom user model with AbstractUser

Define CustomUser class

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Inherit AbstractUser

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Add custom fields/methods

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Update settings.py: AUTH_USER_MODEL

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Run migrations

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Use CustomUser in app

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Authentication and user management with new model

This flow shows how to create a custom user model by extending AbstractUser, update settings, migrate, and then use the new user model.

Execution Sample

Django

from django.contrib.auth.models import AbstractUser
from django.db import models

class CustomUser(AbstractUser):
    age = models.PositiveIntegerField(null=True, blank=True)

# settings.py
AUTH_USER_MODEL = 'myapp.CustomUser'

Defines a CustomUser model extending AbstractUser with an extra 'age' field and sets it as the user model in settings.

Execution Table

Step	Action	Code/Setting	Result/Effect
1	Define CustomUser class	class CustomUser(AbstractUser): age = models.PositiveIntegerField(null=True, blank=True)	CustomUser model created with all AbstractUser fields plus 'age'
2	Update settings.py	AUTH_USER_MODEL = 'myapp.CustomUser'	Django uses CustomUser as the user model
3	Run makemigrations	python manage.py makemigrations	Migration file created for CustomUser model
4	Run migrate	python manage.py migrate	Database tables updated to include CustomUser
5	Use CustomUser in app	from django.contrib.auth import get_user_model	CustomUser is used for authentication and user management
6	Exit	N/A	Setup complete, app uses CustomUser

💡 Setup stops after migrations and app uses CustomUser for authentication

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	After Step 4	Final
CustomUser	Not defined	Defined with AbstractUser + age	Same	Same	Same	Same
AUTH_USER_MODEL	Default 'auth.User'	Default	'myapp.CustomUser'	'myapp.CustomUser'	'myapp.CustomUser'	'myapp.CustomUser'
Migration files	None	None	None	New migration created	Applied to DB	Applied to DB

Key Moments - 3 Insights

Why must AUTH_USER_MODEL be set before the first migrate?

Because Django creates the user table on first migrate; changing AUTH_USER_MODEL later causes conflicts. See execution_table steps 2-4.

Can I add fields directly to AbstractUser?

No, you create a subclass (CustomUser) to add fields. AbstractUser is a base class. See step 1 in execution_table.

How do I reference the custom user model in code?

Use get_user_model() to get the current user model, ensuring compatibility. See step 5 in execution_table.

Visual Quiz - 3 Questions

Look at the execution table, what happens at step 3?

A Run migrate to apply database changes

B Define the CustomUser class

C Create migration files for CustomUser

D Update settings.py to set AUTH_USER_MODEL

💡 Hint

Check the 'Action' and 'Code/Setting' columns at step 3 in execution_table

At which step does Django start using the CustomUser model for authentication?

A Step 2

B Step 5

C Step 4

D Step 1

💡 Hint

Look for when the app imports and uses the user model in execution_table

If you forget to set AUTH_USER_MODEL before migrating, what is the likely result?

A Django uses the default User model and migrations conflict later

B CustomUser is used anyway without issues

C Migrations run faster

D Django raises an error immediately

💡 Hint

Refer to key_moments about setting AUTH_USER_MODEL before first migrate

Concept Snapshot

Custom user model with AbstractUser:
- Create a class inheriting AbstractUser
- Add custom fields as needed
- Set AUTH_USER_MODEL in settings.py
- Run makemigrations and migrate
- Use get_user_model() to access the user model
- Must set AUTH_USER_MODEL before first migrate

Full Transcript

To create a custom user model in Django, define a class that inherits from AbstractUser and add any extra fields you want. Then, update your settings.py file to set AUTH_USER_MODEL to point to your new model. After that, run makemigrations and migrate to create the necessary database tables. Finally, use get_user_model() in your code to reference the custom user model. Remember, you must set AUTH_USER_MODEL before running your first migrate to avoid conflicts.

Practice

1. What is the main reason to create a custom user model by extending AbstractUser in Django?

easy

A. To add extra fields or change user behavior while keeping Django's default features

B. To remove all default user features and start from scratch

C. To automatically create admin users without configuration

D. To avoid using migrations in the project

Solution

1. Step 1: Understand AbstractUser purpose

   AbstractUser provides Django's default user fields and behavior as a base class.

2. Step 2: Reason for extending AbstractUser

   Extending it allows adding custom fields or changing behavior without losing built-in features.

3. Final Answer:

   To add extra fields or change user behavior while keeping Django's default features -> Option A

4. Quick Check:

   Custom user model = Extend AbstractUser for extra fields [OK]

Hint: AbstractUser keeps defaults; extend it to add fields [OK]

Common Mistakes:

• Thinking AbstractUser removes default features
• Believing custom user models skip migrations
• Assuming admin users are auto-created

2. Which of the following is the correct way to declare a custom user model by extending AbstractUser in Django?

easy

A. class CustomUser(AbstractBaseUser):\n pass

B. class CustomUser(User):\n pass

C. class CustomUser(models.Model):\n pass

D. class CustomUser(AbstractUser):\n pass

Solution

1. Step 1: Identify correct base class

   The question asks for extending AbstractUser, so the class must inherit from it.

2. Step 2: Check syntax correctness

   class CustomUser(AbstractUser):\n pass correctly defines class CustomUser(AbstractUser): pass which is valid syntax.

3. Final Answer:

   class CustomUser(AbstractUser):\n pass -> Option D

4. Quick Check:

   Extend AbstractUser with class CustomUser(AbstractUser) [OK]

Hint: Use AbstractUser as base class for custom user model [OK]

Common Mistakes:

• Using User instead of AbstractUser as base
• Inheriting directly from models.Model without user features
• Confusing AbstractBaseUser with AbstractUser

3. Given this custom user model:

from django.contrib.auth.models import AbstractUser
from django.db import models

class CustomUser(AbstractUser):
    age = models.PositiveIntegerField(null=True, blank=True)

# settings.py
AUTH_USER_MODEL = 'myapp.CustomUser'

What will happen if you try to create a user without specifying age?

medium

A. User creation fails due to missing age field

B. User is created successfully with age set to None

C. User is created but age defaults to 0

D. Error because age is required

Solution

1. Step 1: Analyze age field definition

   Age is defined as PositiveIntegerField with null=True and blank=True, so it is optional.

2. Step 2: Understand user creation behavior

   Since age is optional, creating a user without it sets age to None (null in database).

3. Final Answer:

   User is created successfully with age set to None -> Option B

4. Quick Check:

   Optional field with null=True allows missing value [OK]

Hint: null=True means field can be empty on creation [OK]

Common Mistakes:

• Assuming blank=True means field is required
• Thinking missing fields default to 0 automatically
• Confusing null=True with default values

4. You created a custom user model extending AbstractUser and set AUTH_USER_MODEL in settings. After running migrations, you get an error about conflicting user models. What is the most likely cause?

medium

A. You set AUTH_USER_MODEL after initial migrations were created

B. You forgot to import AbstractUser in your model

C. You did not define a primary key in your custom user model

D. You used AbstractBaseUser instead of AbstractUser

Solution

1. Step 1: Understand migration timing

   If AUTH_USER_MODEL is set after initial migrations, Django creates default user tables causing conflicts.

2. Step 2: Identify cause of conflict error

   The conflict arises because two user models exist: default and custom, due to late setting of AUTH_USER_MODEL.

3. Final Answer:

   You set AUTH_USER_MODEL after initial migrations were created -> Option A

4. Quick Check:

   Set AUTH_USER_MODEL before first migration [OK]

Hint: Set AUTH_USER_MODEL before first migration to avoid conflicts [OK]

Common Mistakes:

• Ignoring migration order importance
• Assuming import errors cause this conflict
• Confusing AbstractUser with AbstractBaseUser issues

5. You want to add a bio text field to your custom user model extending AbstractUser. You also want to display this bio in Django admin user list view. Which steps should you follow?

hard

A. Add bio field to model, override save() to print bio

B. Add bio field to model, no admin changes needed

C. Add bio field to model, register custom user admin with list_display including 'bio'

D. Add bio field to model, create a new admin site

Solution

1. Step 1: Add bio field to custom user model

   Define bio = models.TextField(blank=True, null=True) in your model to store user bios.

2. Step 2: Customize admin to show bio

   Register your custom user model admin and set list_display = ('username', 'email', 'bio') to show bio in list view.

3. Final Answer:

   Add bio field to model, register custom user admin with list_display including 'bio' -> Option C

4. Quick Check:

   Model field + admin list_display shows field [OK]

Hint: Add field + update admin list_display to show it [OK]

Common Mistakes:

• Forgetting to update admin list_display
• Overriding save() unnecessarily
• Creating new admin site instead of customizing existing