Django QuerySets: Introduction and Using get()

A QuerySet is a collection of data retrieved from the database. You can think of it as a list of objects.
QuerySets make it easier to get only the data you need by letting you filter, sort, and organize your data early on before actually fetching it from the database.

In this article, we will learn how to get data from a model into a QuerySet using get method:

get() Method: Retrieve a Single Object

The get() method returns exactly one object that matches the conditions you provide. It is useful when you expect only one result.

If no object matches, Django raises a DoesNotExist exception. If more than one object matches, it raises a MultipleObjectsReturned exception.

Syntax

Model.objects.get(**kwargs)

• Model is your Django model.
• kwargs are the conditions used to find the object.

Example: Using get() with a Book Model

Suppose we have a Book model with fields like title and author. To get the book titled "The Great Gatsby":

from app.models import Book

try:
    book = Book.objects.get(title='The Great Gatsby')
    # Use the book object here
except Book.DoesNotExist:
    print("No book found with that title.")
except Book.MultipleObjectsReturned:
    print("Multiple books found with that title.")

Using Multiple Conditions (AND)

You can provide multiple filters to narrow down results. For example, suppose we have multiple books with title "The Great Gatsby", but we only need results for the book to be written by author "F. Scott Fitzgerald", then we provide multiple query conditions:

try:
    book = Book.objects.get(title='The Great Gatsby', author='F. Scott Fitzgerald')
except Book.DoesNotExist:
    print("No matching book found.")
except Book.MultipleObjectsReturned:
    print("More than one book matches your query.")

Django treats these conditions as an AND operation, returning the object that matches all conditions.

Using Primary Key with get()

Fetching objects by their primary key (usually id) is common:

book = Book.objects.get(pk=1) # Get book with primary key 1

Practical Uses of get()

• Authenticating users by username or email.
• Retrieving records using unique fields like primary keys.
• Getting exact matches when you expect one record.

Using get() in the Django Shell

The Django shell is an interactive Python environment that lets you experiment with your Django models and QuerySets in real-time. It’s a great tool for testing database queries, exploring your data, and debugging without needing to write views or templates first.

Example: Fetching a Book Object Using get()

Consider the book model we created earlier and we need to fetch data from it using Python Shell, here's how we can do it:

1. Activate the Shell:

python manage.py shell

2. Use the following commands:

>>> from app.models import Book

>>> book = Book.objects.get(id=2)

>>> print(book)

This should print the details of book with id = 2.

Note: If no book with id=3 exists, a DoesNotExist exception will be raised; if multiple entries matched (unlikely with primary keys), a MultipleObjectsReturned exception would occur.