django-model

Formal Definition

A Django Model is a Python class that defines the structure and behavior of data stored in the database, acting as the definitive source of information about your data using Django’s Object-Relational Mapper (ORM).

Explanation

Instead of writing raw SQL to create tables and manage data, you write Python classes. A Model represents a single database table, and its attributes represent the columns. Django automatically translates this class into the corresponding SQL.

How It Works

Define a class inheriting from django.db.models.Model.
Define class attributes as fields (e.g., models.CharField).
Run makemigrations to generate migration files based on the model.
Run migrate to apply the changes to the database schema.
Use the model’s Manager (e.g., Model.objects) to query the database.

Visual Explanation

graph TD
  A[Model Class in Python] -->|makemigrations| B(Migration File)
  B -->|migrate| C[(Database Table)]

Mental Model & Analogy

Think of a Model as a blueprint or a mold. If you want to make toy cars (database rows), you first design the mold (the Model) specifying it has 4 wheels, a color, and a shape. Django uses this mold to stamp out data in the database.

Implementation & Examples

from django.db import models
 
class Student(models.Model):
    name = models.CharField(max_length=100)
    age = models.IntegerField()

Key Properties

Subclasses django.db.models.Model.
Fields map to database columns.
Provides an automatic API to query the database.

Connections

Built from: Django ORM — the system that powers models.
Builds into: Django Migration — models generate migrations.
Related: Django View — views interact with models.
Related: Django Form — ModelForms are generated from models.

Edge Cases & Gotchas

Changing a model requires making and applying migrations; the database doesn’t magically update.
N+1 query problems can occur if relationships are not queried efficiently using select_related or prefetch_related.

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