Response model exclude and include in FastAPI - Mini Project: Build & Apply

FastAPI Response Model Exclude and Include

📖 Scenario: You are building a simple API for a bookstore. You want to control which book details are sent back to users in different situations.

🎯 Goal: Create a FastAPI app that returns book data. Use response_model with exclude and include options to control which fields appear in the response.

📋 What You'll Learn

Create a Pydantic model Book with fields title, author, year, and price

Create a FastAPI app with two routes: one that excludes price from the response, and one that includes only title and author

Use response_model with response_model_exclude and response_model_include parameters

Test that the API returns the correct fields for each route

💡 Why This Matters

🌍 Real World

APIs often need to send different views of the same data to different users or clients. Controlling response fields helps keep data minimal and secure.

💼 Career

Knowing how to customize API responses is important for backend developers working with FastAPI or similar frameworks to build efficient and secure web services.

1

Create the Book model

Create a Pydantic model called Book with the fields title (str), author (str), year (int), and price (float).

FastAPI

from fastapi import FastAPI
from pydantic import BaseModel

app = FastAPI()

# Create the Book model with title, author, year, and price
# Your code here

Need a hint?

Use class Book(BaseModel): and define each field with its type.

2

Create a sample book data

Create a variable called sample_book and assign it a Book instance with title='The FastAPI Guide', author='Alex', year=2023, and price=29.99.

FastAPI

from fastapi import FastAPI
from pydantic import BaseModel

app = FastAPI()

class Book(BaseModel):
    title: str
    author: str
    year: int
    price: float

# Create sample_book with the given values
# Your code here

Need a hint?

Create sample_book by calling Book(...) with the exact values.

3

Create route excluding the price field

Create a GET route at /book_no_price that returns sample_book. Use response_model=Book and set response_model_exclude={'price'} to exclude the price field from the response.

FastAPI

from fastapi import FastAPI
from pydantic import BaseModel

app = FastAPI()

class Book(BaseModel):
    title: str
    author: str
    year: int
    price: float

sample_book = Book(title='The FastAPI Guide', author='Alex', year=2023, price=29.99)

# Create GET route /book_no_price with response_model=Book and exclude price
# Your code here

Need a hint?

Use @app.get decorator with response_model=Book and response_model_exclude={'price'}.

4

Create route including only title and author

Create a GET route at /book_title_author that returns sample_book. Use response_model=Book and set response_model_include={'title', 'author'} to include only the title and author fields in the response.

FastAPI

from fastapi import FastAPI
from pydantic import BaseModel

app = FastAPI()

class Book(BaseModel):
    title: str
    author: str
    year: int
    price: float

sample_book = Book(title='The FastAPI Guide', author='Alex', year=2023, price=29.99)

@app.get('/book_no_price', response_model=Book, response_model_exclude={'price'})
def get_book_no_price():
    return sample_book

# Create GET route /book_title_author with response_model=Book and include only title and author
# Your code here

Need a hint?

Use @app.get with response_model_include={'title', 'author'} to include only those fields.