Optional query parameters in FastAPI - Mini Project: Build & Apply

Optional Query Parameters in FastAPI

📖 Scenario: You are building a simple web API for a bookstore. You want to allow users to search for books by title. Additionally, users can optionally filter the search results by author name if they want.

🎯 Goal: Create a FastAPI app with an endpoint /books/ that accepts a required query parameter title and an optional query parameter author. The endpoint should return a JSON list of books matching the title and, if provided, the author.

📋 What You'll Learn

Create a FastAPI app instance named app

Define a GET endpoint at /books/

Use a required query parameter title of type str

Use an optional query parameter author of type str with default null

Return a filtered list of books matching the title and optionally the author

💡 Why This Matters

🌍 Real World

APIs often need to accept optional filters to let users narrow down search results without requiring all filters.

💼 Career

Understanding optional query parameters is essential for backend developers building flexible and user-friendly APIs.

1

Create the initial data list of books

Create a list called books with these dictionaries exactly: {'title': 'The Hobbit', 'author': 'J.R.R. Tolkien'}, {'title': '1984', 'author': 'George Orwell'}, {'title': 'The Silmarillion', 'author': 'J.R.R. Tolkien'}

FastAPI

# Create the list of books with exact entries
# Your code here

Need a hint?

Use a list of dictionaries. Each dictionary has keys 'title' and 'author'.

2

Create the FastAPI app and import required modules

Import FastAPI from fastapi and create an app instance called app

FastAPI

books = [
    {'title': 'The Hobbit', 'author': 'J.R.R. Tolkien'},
    {'title': '1984', 'author': 'George Orwell'},
    {'title': 'The Silmarillion', 'author': 'J.R.R. Tolkien'}
]

# Import FastAPI and create app instance
# Your code here

Need a hint?

Use from fastapi import FastAPI and then app = FastAPI().

3

Define the GET endpoint with required and optional query parameters

Define a GET endpoint /books/ using @app.get("/books/"). Create a function read_books with parameters title: str and author: str | null = null to accept required title and optional author query parameters.

FastAPI

from fastapi import FastAPI

books = [
    {'title': 'The Hobbit', 'author': 'J.R.R. Tolkien'},
    {'title': '1984', 'author': 'George Orwell'},
    {'title': 'The Silmarillion', 'author': 'J.R.R. Tolkien'}
]

app = FastAPI()

# Define GET endpoint /books/ with parameters title and optional author
# Your code here

Need a hint?

Use @app.get("/books/") and define read_books with parameters title: str and author: str | null = null.

4

Filter and return books matching title and optional author

Inside read_books, create a list results that includes books from books where book['title'] contains title (case insensitive). If author is not null, further filter results to include only books where book['author'] contains author (case insensitive). Return results.

FastAPI

from fastapi import FastAPI

books = [
    {'title': 'The Hobbit', 'author': 'J.R.R. Tolkien'},
    {'title': '1984', 'author': 'George Orwell'},
    {'title': 'The Silmarillion', 'author': 'J.R.R. Tolkien'}
]

app = FastAPI()

@app.get("/books/")
def read_books(title: str, author: str | null = null):
    # Filter books by title and optional author
    # Your code here

Need a hint?

Use list comprehensions to filter books by title and optionally by author. Use str.lower() for case-insensitive matching.