Custom serializer fields in Django - Mini Project: Build & Apply

Custom Serializer Fields in Django REST Framework

📖 Scenario: You are building a simple API for a bookstore. Each book has a title and a price stored as an integer number of cents. You want to show the price in dollars with two decimal places in the API response.

🎯 Goal: Create a Django REST Framework serializer with a custom field that converts the price from cents (integer) to a formatted string in dollars (e.g., '12.99').

📋 What You'll Learn

Create a dictionary called book_data with keys 'title' and 'price_cents' and values 'Django for Beginners' and 2599 respectively.

Create a class called PriceField that subclasses serializers.Field.

Implement the to_representation method in PriceField to convert cents to a string in dollars with two decimals.

Create a serializer class called BookSerializer that uses PriceField for the price field and includes the title field.

💡 Why This Matters

🌍 Real World

APIs often need to present data in a format that is easy for users to understand. Custom serializer fields let you control how data is shown without changing the database.

💼 Career

Knowing how to write custom serializer fields is useful for backend developers working with Django REST Framework to build clean, user-friendly APIs.

1

Create the initial book data dictionary

Create a dictionary called book_data with keys 'title' and 'price_cents' and values 'Django for Beginners' and 2599 respectively.

Django

# Create the book_data dictionary with title and price_cents
# Your code here

Need a hint?

Use curly braces to create a dictionary with the exact keys and values.

2

Create a custom serializer field class

Create a class called PriceField that subclasses serializers.Field.

Django

book_data = {'title': 'Django for Beginners', 'price_cents': 2599}

from rest_framework import serializers

# Create PriceField subclassing serializers.Field
# Your code here

Need a hint?

Define a class with the exact name PriceField and inherit from serializers.Field.

3

Implement the to_representation method

Inside the PriceField class, implement the to_representation method that takes value (price in cents) and returns a string formatted as dollars with two decimals (e.g., '25.99').

Django

book_data = {'title': 'Django for Beginners', 'price_cents': 2599}

from rest_framework import serializers

class PriceField(serializers.Field):
    # Implement to_representation method here
    # Your code here

Need a hint?

Divide the integer value by 100 and format it as a string with two decimal places using an f-string.

4

Create the BookSerializer using the custom field

Create a serializer class called BookSerializer that subclasses serializers.Serializer. Add a title field as serializers.CharField() and a price field using the custom PriceField.

Django

book_data = {'title': 'Django for Beginners', 'price_cents': 2599}

from rest_framework import serializers

class PriceField(serializers.Field):
    def to_representation(self, value):
        return f"{value / 100:.2f}"

# Create BookSerializer with title and price fields
# Your code here

Need a hint?

Define the serializer class with the exact name and add the two fields as shown. Use source='price_cents' for the price field to map to the correct key in the data.