Teardown hooks in Flask - Mini Project: Build & Apply

Using Teardown Hooks in Flask

📖 Scenario: You are building a simple Flask web app that needs to clean up resources after each request. This is important to avoid resource leaks, like open database connections.

🎯 Goal: Learn how to use Flask's teardown_appcontext decorator to run cleanup code automatically after each request finishes.

📋 What You'll Learn

Create a Flask app instance named app

Define a function called close_db that prints 'Closing database connection' when called

Register close_db as a teardown hook using @app.teardown_appcontext

Create a simple route / that returns 'Hello, Flask!'

💡 Why This Matters

🌍 Real World

Teardown hooks help clean up resources like database connections or files after each web request, preventing resource leaks.

💼 Career

Understanding teardown hooks is important for backend developers to write robust Flask applications that manage resources efficiently.

1

Create the Flask app instance

Import Flask from flask and create a Flask app instance called app.

Flask

# Import Flask and create app instance
# Your code here

Need a hint?

Use Flask(__name__) to create the app instance.

2

Define the teardown function

Define a function called close_db that takes one argument exception and prints 'Closing database connection' inside the function.

Flask

from flask import Flask
app = Flask(__name__)

# Define close_db function
# Your code here

Need a hint?

The function must accept exception even if you don't use it.

3

Register the teardown hook

Use the @app.teardown_appcontext decorator to register the close_db function as a teardown hook.

Flask

from flask import Flask
app = Flask(__name__)

# Register close_db as teardown hook
# Your code here
def close_db(exception):
    print('Closing database connection')

Need a hint?

Place the decorator @app.teardown_appcontext right above the close_db function.

4

Add a simple route

Create a route for / using @app.route('/') that defines a function index returning the string 'Hello, Flask!'.

Flask

from flask import Flask
app = Flask(__name__)

@app.teardown_appcontext
def close_db(exception):
    print('Closing database connection')

# Create route for '/' that returns 'Hello, Flask!'
# Your code here

Need a hint?

Use @app.route('/') decorator and define index function returning the greeting string.