Introduction to Django Models

What a Model Is

A Django model is a Python class that inherits from models.Model. Each attribute you define on it becomes a column in the database table Django creates for it.

Note: Model class names are singular and CamelCase, e.g. Book, not Books or book.

Example: What a Model Is

A Django model is a Python class that inherits from models.Model. Each attribute you define on it becomes a column in the database table Django creates for it.

from django.db import models


class Book(models.Model):
    title = models.CharField(max_length=200)
    pages = models.IntegerField()

    def __str__(self):
        return self.title

Where Models Live

Every Django app has its own models.py file. Django reads every model in every INSTALLED_APPS app to figure out what tables the whole project needs.

Warning: The app that defines the model must be listed in INSTALLED_APPS or Django won't detect it.

Example: Where Models Live

Every Django app has its own models.py file. Django reads every model in every INSTALLED_APPS app to figure out what tables the whole project needs.

# myapp/models.py
from django.db import models


class Student(models.Model):
    name = models.CharField(max_length=100)
    grade = models.IntegerField()

From Model to Table

Defining a model class doesn't create the database table by itself. Django needs a migration to translate the Python class into real SQL that builds the table.

Note: Always run makemigrations then migrate right after adding or changing a model.

Example: From Model to Table

Defining a model class doesn't create the database table by itself. Django needs a migration to translate the Python class into real SQL that builds the table.

python manage.py makemigrations
python manage.py migrate

A Complete Minimal Model

A working model needs at minimum a class name, an inherited base, and at least one field. Django automatically adds an id auto-incrementing primary key for you.

Example: A Complete Minimal Model

A working model needs at minimum a class name, an inherited base, and at least one field. Django automatically adds an id auto-incrementing primary key for you.

from django.db import models


class Task(models.Model):
    title = models.CharField(max_length=150)
    is_done = models.BooleanField(default=False)

    def __str__(self):
        return self.title