Why ORM maps Python to database in Django - See It in Action

Why ORM Maps Python to Database

📖 Scenario: Imagine you are building a simple app to keep track of books in a library. You want to save book details like title and author in a database, but you want to work with Python code instead of writing raw database commands.

🎯 Goal: You will create a Django model to represent books, configure a simple setting, write a query to get books, and complete the setup to see how Python code connects to the database using ORM.

📋 What You'll Learn

Create a Django model class called Book with fields title and author

Add a configuration variable MAX_BOOKS set to 100

Write a query using Django ORM to get all books with titles longer than 5 characters

Complete the model with a __str__ method to return the book title

💡 Why This Matters

🌍 Real World

ORM lets developers work with databases using Python code instead of SQL. This makes apps easier to build and maintain.

💼 Career

Understanding ORM is key for backend developers working with Django or similar frameworks to handle data storage efficiently.

1

Create the Book model

Create a Django model class called Book with two fields: title as a CharField with max length 100, and author as a CharField with max length 50.

Django

# Your code here

Need a hint?

Use models.CharField for text fields and set max_length as instructed.

2

Add a configuration variable

Add a variable called MAX_BOOKS and set it to 100 below the model class.

Django

from django.db import models

class Book(models.Model):
    title = models.CharField(max_length=100)
    author = models.CharField(max_length=50)

# Your code here

Need a hint?

Just create a variable with the exact name and value.

3

Write a Django ORM query

Write a Django ORM query called long_title_books that gets all Book objects with title longer than 5 characters. Import Length from django.db.models.functions and use annotate(title_length=Length('title')) with filter(title_length__gt=5).

Django

from django.db import models

class Book(models.Model):
    title = models.CharField(max_length=100)
    author = models.CharField(max_length=50)

MAX_BOOKS = 100

# Your code here

Need a hint?

Import Length from django.db.models.functions and use Book.objects.annotate(title_length=Length('title')).filter(title_length__gt=5).

4

Add the __str__ method

Add a __str__ method inside the Book model class that returns the title of the book.

Django

from django.db import models
from django.db.models.functions import Length

class Book(models.Model):
    title = models.CharField(max_length=100)
    author = models.CharField(max_length=50)

    # Your code here

MAX_BOOKS = 100

long_title_books = Book.objects.annotate(title_length=Length('title')).filter(title_length__gt=5)

Need a hint?

The __str__ method helps show the book title when you print or view the object.