FastAPI vs Flask vs Django comparison - Hands-On Comparison

FastAPI vs Flask vs Django Comparison

📖 Scenario: You are building a simple web API to manage a list of books. You want to understand how to create this API using three popular Python web frameworks: FastAPI, Flask, and Django. This project will guide you step-by-step to create a basic API endpoint in FastAPI, then compare its structure and features with Flask and Django.

🎯 Goal: Create a FastAPI application with a simple endpoint to list books. Learn how to set up initial data, configure a route, implement the main logic to return data, and finalize the app. Understand the differences in setup and usage compared to Flask and Django.

📋 What You'll Learn

Create a list of books as initial data

Add a configuration variable for API version

Implement a GET endpoint to return the list of books

Complete the FastAPI app with proper route and run configuration

💡 Why This Matters

🌍 Real World

Web APIs are common in many applications like online stores, social media, and data services. FastAPI, Flask, and Django are popular tools to build these APIs efficiently.

💼 Career

Understanding these frameworks helps you work on backend development roles, build scalable APIs, and collaborate with frontend teams.

1

DATA SETUP: Create the initial list of books

Create a list called books with these exact dictionaries: {'id': 1, 'title': '1984', 'author': 'George Orwell'} and {'id': 2, 'title': 'Brave New World', 'author': 'Aldous Huxley'}.

FastAPI

# Create the list of books with two dictionaries
# Your code here

Hint

Use a list with two dictionaries exactly as shown.

2

CONFIGURATION: Add API version variable

Add a string variable called api_version and set it to 'v1'.

FastAPI

books = [
    {'id': 1, 'title': '1984', 'author': 'George Orwell'},
    {'id': 2, 'title': 'Brave New World', 'author': 'Aldous Huxley'}
]
# Add the api_version variable below
# Your code here

Hint

Just create a variable named api_version and assign the string 'v1'.

3

CORE LOGIC: Create FastAPI app and GET endpoint

Import FastAPI from fastapi. Create an app instance called app. Use @app.get decorator with path f'/api/{api_version}/books' to define a function get_books that returns the books list.

FastAPI

books = [
    {'id': 1, 'title': '1984', 'author': 'George Orwell'},
    {'id': 2, 'title': 'Brave New World', 'author': 'Aldous Huxley'}
]

api_version = 'v1'

# Import FastAPI and create app instance
# Define GET endpoint to return books
# Your code here

Hint

Remember to import FastAPI, create app, and use the decorator with the formatted path.

4

COMPLETION: Add code to run the FastAPI app

Add the standard if __name__ == '__main__': block. Inside it, import uvicorn and run the app with uvicorn.run(app, host='127.0.0.1', port=8000).

FastAPI

from fastapi import FastAPI

books = [
    {'id': 1, 'title': '1984', 'author': 'George Orwell'},
    {'id': 2, 'title': 'Brave New World', 'author': 'Aldous Huxley'}
]

api_version = 'v1'

app = FastAPI()

@app.get(f"/api/{api_version}/books")
def get_books():
    return books

# Add code to run the app with uvicorn
# Your code here

Hint

This block lets you run the FastAPI app directly with Python.

Practice

1. Which framework is best known for being modern, fast, and supporting automatic type checking for APIs?

easy

A. Flask

B. Pyramid

C. Django

D. FastAPI

Solution

1. Step 1: Understand framework features

   FastAPI is designed to be modern and fast, with built-in support for Python type hints to validate and document APIs automatically.

2. Step 2: Compare with other frameworks

   Flask is minimal and easy to start but lacks built-in type checking. Django is full-featured but more heavyweight and not focused on type checking.

3. Final Answer:

   FastAPI -> Option D

4. Quick Check:

   Modern + fast + type checking = FastAPI [OK]

Hint: Modern + fast + type hints = FastAPI [OK]

Common Mistakes:

• Confusing Flask's simplicity with FastAPI's speed
• Thinking Django has built-in type checking
• Choosing Pyramid which is less common

2. Which of the following is the correct way to create a simple route in Flask?

easy

A. app.route('/')(def home(): return 'Hello')

B. @app.route('/')
def home():
return 'Hello'

C. app.get('/')
def home():
return 'Hello'

D. @app.get('/')
def home():
return 'Hello'

Solution

1. Step 1: Recall Flask route syntax

   In Flask, routes are created using the @app.route decorator above a function.

2. Step 2: Identify correct decorator and syntax

   @app.route('/') def home(): return 'Hello' uses @app.route('/') with proper Python function definition and indentation, which is correct Flask syntax.

3. Final Answer:

   @app.route('/') def home(): return 'Hello' -> Option B

4. Quick Check:

   Flask route decorator = @app.route [OK]

Hint: Flask uses @app.route decorator, not app.route() call [OK]

Common Mistakes:

• Missing @ symbol before decorator
• Using app.get instead of app.route in Flask
• Incorrect indentation or function syntax

3. Given this FastAPI code snippet, what will be the output when accessing /items/5?

from fastapi import FastAPI
app = FastAPI()

@app.get('/items/{item_id}')
async def read_item(item_id: int):
    return {'item_id': item_id * 2}

medium

A. {'item_id': 10}

B. {'item_id': '5'}

C. {'item_id': 5}

D. Error: item_id must be a string

Solution

1. Step 1: Understand path parameter and type

   The route expects an integer item_id. When accessing /items/5, item_id is 5 as int.

2. Step 2: Calculate returned value

   The function returns a dictionary with 'item_id' key and value item_id * 2, so 5 * 2 = 10.

3. Final Answer:

   {'item_id': 10} -> Option A

4. Quick Check:

   5 * 2 = 10 output [OK]

Hint: Multiply path param by 2 as int to get output [OK]

Common Mistakes:

• Assuming item_id is string, not int
• Returning original item_id instead of multiplied
• Expecting error due to type mismatch

4. Identify the error in this Django view code snippet:

from django.http import HttpResponse

def home(request):
return HttpResponse('Hello')

medium

A. Indentation error in function body

B. HttpResponse should be replaced with JsonResponse

C. Missing import for HttpRequest

D. Function name must be capitalized

Solution

1. Step 1: Check Python syntax rules

   Python requires the function body to be indented under the def line.

2. Step 2: Identify indentation problem

   The return statement is not indented, causing a syntax error.

3. Final Answer:

   Indentation error in function body -> Option A

4. Quick Check:

   Python function body must be indented [OK]

Hint: Check indentation under def for Python functions [OK]

Common Mistakes:

• Ignoring indentation errors
• Thinking import is missing
• Assuming JsonResponse is mandatory

5. You want to build a large, complex web app with built-in admin, user authentication, and database ORM. Which framework is the best choice and why?

hard

A. FastAPI, because it is the fastest and has built-in admin

B. Flask, because it is minimal and easy to add features manually

C. Django, because it is full-featured with admin, auth, and ORM included

D. FastAPI, because it supports async and type checking

Solution

1. Step 1: Identify requirements for large complex app

   Needs built-in admin panel, user authentication, and ORM for database management.

2. Step 2: Match framework features to requirements

   Django provides all these features out of the box, making it ideal for large apps. FastAPI and Flask require extra setup for these.

3. Final Answer:

   Django, because it is full-featured with admin, auth, and ORM included -> Option C

4. Quick Check:

   Full features for big apps = Django [OK]

Hint: Full features + admin + auth = Django [OK]

Common Mistakes:

• Choosing FastAPI for admin features it lacks
• Thinking Flask has built-in admin
• Ignoring Django's batteries-included approach