Migrating to async Flask - Mini Project: Build & Apply

Migrating to async Flask

📖 Scenario: You have a simple Flask web app that handles requests synchronously. To improve performance and handle multiple requests efficiently, you want to migrate your Flask routes to use asynchronous functions.

🎯 Goal: Convert a basic synchronous Flask route into an asynchronous route using async def and await syntax, while keeping the app functional.

📋 What You'll Learn

Create a Flask app with a synchronous route

Add an async helper function to simulate an async task

Convert the route handler to an async function using async def

Use await to call the async helper inside the route

Run the Flask app with async support

💡 Why This Matters

🌍 Real World

Modern web apps often need to handle many requests efficiently. Using async Flask routes helps improve performance by not blocking the server while waiting for slow operations like network calls or database queries.

💼 Career

Understanding how to migrate synchronous Flask apps to async is valuable for backend developers working on scalable web services and APIs.

1

Create a basic synchronous Flask app

Create a Flask app by importing Flask from flask and instantiate it as app. Then define a synchronous route handler function called hello for the path "/" that returns the string "Hello, World!".

Flask

# Your code here

Need a hint?

Start by importing Flask and creating an app instance. Then use @app.route("/") to define the route and a normal def function to return the greeting.

2

Add an async helper function

Add an asynchronous helper function called async_task that uses async def and inside it, use import asyncio and await asyncio.sleep(1) to simulate a 1-second async delay. The function should then return the string "Async task complete".

Flask

from flask import Flask

app = Flask(__name__)

@app.route("/")
def hello():
    return "Hello, World!"

# Your code here

Need a hint?

Define an async def function and use await asyncio.sleep(1) to simulate waiting asynchronously.

3

Convert the route handler to async and call the async helper

Change the hello route handler to an asynchronous function by replacing def with async def. Inside it, call the async_task function using await and store the result in a variable called message. Then return the message variable.

Flask

from flask import Flask
import asyncio

app = Flask(__name__)

@app.route("/")
# Convert this function to async and call async_task
# Your code here

async def async_task():
    await asyncio.sleep(1)
    return "Async task complete"

Need a hint?

Change the route function to async def and use await async_task() to get the message.

4

Run the Flask app with async support

Add the standard Flask app runner code under if __name__ == '__main__': to run the app with app.run(debug=True). This will start the Flask development server supporting async routes.

Flask

from flask import Flask
import asyncio

app = Flask(__name__)

@app.route("/")
async def hello():
    message = await async_task()
    return message

async def async_task():
    await asyncio.sleep(1)
    return "Async task complete"

# Your code here

Need a hint?

Add the usual Flask app runner block to start the server.