Trailing slash behavior in Flask - Mini Project: Build & Apply

Trailing Slash Behavior in Flask Routes

📖 Scenario: You are building a simple Flask web app that has two pages: a homepage and an about page. You want to understand how Flask handles URLs with and without trailing slashes.

🎯 Goal: Create two Flask routes: one for the homepage at / and one for the about page at /about/. Learn how Flask redirects URLs when the trailing slash is missing or present.

📋 What You'll Learn

Create a Flask app instance named app

Define a route for the homepage at / that returns the text 'Welcome to the homepage!'

Define a route for the about page at /about/ that returns the text 'About us page'

Observe how Flask handles requests to /about without the trailing slash

💡 Why This Matters

🌍 Real World

Web developers often need to control URL formats for SEO and user experience. Understanding trailing slash behavior helps avoid broken links and unexpected redirects.

💼 Career

Knowing how Flask handles trailing slashes is important for backend developers building web applications to ensure clean and consistent URLs.

1

Create the Flask app and homepage route

Import Flask from flask and create a Flask app instance called app. Then define a route for the homepage at / that returns the string 'Welcome to the homepage!'.

Flask

# Your code here

Need a hint?

Start by importing Flask and creating the app instance. Then use @app.route('/') to define the homepage route.

2

Add a trailing slash route for the about page

Add a new route to app for the URL /about/ (with a trailing slash). Define a function called about that returns the string 'About us page'.

Flask

from flask import Flask

app = Flask(__name__)

@app.route('/')
def home():
    return 'Welcome to the homepage!'

# Add the about page route below
# Your code here

Need a hint?

Use @app.route('/about/') to define the about page route with a trailing slash.

3

Test Flask's trailing slash redirect behavior

Explain what happens if a user visits /about (without the trailing slash) in their browser. Add a comment in the code describing Flask's automatic redirect behavior for routes defined with a trailing slash.

Flask

from flask import Flask

app = Flask(__name__)

@app.route('/')
def home():
    return 'Welcome to the homepage!'

@app.route('/about/')
def about():
    # Flask will redirect '/about' to '/about/' automatically
    return 'About us page'

Need a hint?

Write a comment inside the about function explaining Flask's redirect from /about to /about/.

4

Add a route without trailing slash and observe behavior

Add a new route for /contact (without trailing slash) that returns 'Contact page'. Add a comment explaining that Flask will NOT redirect if the trailing slash is missing in the route definition.

Flask

from flask import Flask

app = Flask(__name__)

@app.route('/')
def home():
    return 'Welcome to the homepage!'

@app.route('/about/')
def about():
    # Flask automatically redirects '/about' to '/about/' with a 308 redirect
    return 'About us page'

# Add a route for '/contact' without trailing slash
# Your code here

Need a hint?

Define the /contact route without a trailing slash and add a comment about Flask's behavior.