Trailing slash behavior in Flask - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a Flask route that responds to '/home/' with a trailing slash.

Flask

from flask import Flask
app = Flask(__name__)

@app.route('/home[1]')
def home():
    return 'Welcome Home!'

Drag options to blanks, or click blank then click option'

A/

C//

Dhome/

Attempts:

3 left

💡 Hint

Common Mistakes

Leaving out the slash causes Flask to redirect automatically, which might confuse beginners.

The trailing slash '/' in the route decorator means the URL must end with a slash. Flask will redirect '/home' to '/home/' automatically.

2fill in blank

medium

Complete the code to define a Flask route that responds to '/about' without a trailing slash.

Flask

from flask import Flask
app = Flask(__name__)

@app.route('/about[1]')
def about():
    return 'About Page'

Drag options to blanks, or click blank then click option'

A/

C//

Dabout/

Attempts:

3 left

💡 Hint

Common Mistakes

Adding a slash causes Flask to redirect '/about' to '/about/' which is not intended here.

When the route does not have a trailing slash, Flask will not redirect URLs with a slash to this route. The URL must match exactly '/about'.

3fill in blank

hard

Fix the error in the route decorator to correctly handle the URL '/contact/' with a trailing slash.

Flask

from flask import Flask
app = Flask(__name__)

@app.route('/contact[1]')
def contact():
    return 'Contact Us'

Drag options to blanks, or click blank then click option'

B/contact/

C/

D//

Attempts:

3 left

💡 Hint

Common Mistakes

Using double slashes or repeating the route name inside the decorator.

The route should end with a single '/' to indicate a trailing slash. Using '/contact/' twice or no slash causes errors or unexpected behavior.

4fill in blank

hard

Complete the code to create a Flask route that accepts '/profile' without a slash and '/profile/' with a slash, redirecting the slash version to the no-slash version.

Flask

from flask import Flask
app = Flask(__name__)

@app.route('/profile', strict_slashes=[1])
def profile():
    return 'User Profile'

Drag options to blanks, or click blank then click option'

B/

CTrue

DFalse

Attempts:

3 left

💡 Hint

Common Mistakes

Adding a slash in the route string or setting strict_slashes=False disables the redirect behavior.

Setting the route without a trailing slash and strict_slashes=True means Flask will redirect '/profile/' to '/profile'.

5fill in blank

hard

Fill all three blanks to define a Flask route that accepts '/dashboard/' with a trailing slash and disables automatic redirect for missing slash URLs.

Flask

from flask import Flask
app = Flask(__name__)

@app.route('/dashboard[1]', strict_slashes=[2])
def dashboard():
    return 'Dashboard Page'

# Accessing '/dashboard' will [3] redirect to '/dashboard/'

Drag options to blanks, or click blank then click option'

A/

BTrue

Cnot trigger

DFalse

Attempts:

3 left

💡 Hint

Common Mistakes

Setting strict_slashes=True causes Flask to redirect automatically.

Using a trailing slash in the route and strict_slashes=False disables Flask's automatic redirect from '/dashboard' to '/dashboard/'.

Practice

1. In Flask, what happens if you define a route with a trailing slash like @app.route('/home/') and a user visits /home without the slash?

easy

A. Flask returns a 404 Not Found error.

B. Flask serves the /home route without redirecting.

C. Flask redirects the user to /home/ automatically.

D. Flask throws a server error.

Solution

1. Step 1: Understand trailing slash behavior in Flask routes

   Routes defined with a trailing slash expect URLs to end with a slash.

2. Step 2: Check Flask's automatic redirect behavior

   If a user visits the URL without the trailing slash, Flask automatically redirects to the URL with the slash.

3. Final Answer:

   Flask redirects the user to /home/ automatically. -> Option C

4. Quick Check:

   Trailing slash route redirects missing slash URL [OK]

Hint: Trailing slash routes redirect missing slash URLs [OK]

Common Mistakes:

• Thinking Flask serves both URLs without redirect
• Assuming 404 error occurs without slash
• Believing Flask throws server error

2. Which of the following is the correct syntax to define a Flask route that does NOT accept a trailing slash?

easy

A. @app.route('/about/')

B. @app.route('/about//')

C. @app.route('about/')

D. @app.route('/about')

Solution

1. Step 1: Identify correct route syntax without trailing slash

   To define a route that does not accept a trailing slash, the route string should not end with a slash.

2. Step 2: Check each option

   @app.route('/about') uses '/about' without a trailing slash, which is correct syntax.

3. Final Answer:

   @app.route('/about') -> Option D

4. Quick Check:

   Route without trailing slash = no slash in route string [OK]

Hint: No trailing slash means route string ends without slash [OK]

Common Mistakes:

• Adding extra slashes in route string
• Omitting leading slash in route
• Confusing trailing slash with double slashes

3. Given this Flask code:

@app.route('/page/')
def page():
    return 'Page with slash'

What will happen if a user visits /page in their browser?

medium

A. The user sees 'Page with slash' without URL change.

B. The user is redirected to /page/ and sees 'Page with slash'.

C. The user gets a 404 Not Found error.

D. The server crashes with an error.

Solution

1. Step 1: Analyze route definition with trailing slash

   The route '/page/' expects URLs ending with a slash.

2. Step 2: Understand Flask's redirect behavior

   If the user visits '/page' without the slash, Flask redirects to '/page/' automatically and serves the response.

3. Final Answer:

   The user is redirected to /page/ and sees 'Page with slash'. -> Option B

4. Quick Check:

   Trailing slash route redirects missing slash URL [OK]

Hint: Trailing slash route redirects missing slash URL [OK]

Common Mistakes:

• Assuming no redirect happens
• Expecting 404 error on missing slash
• Thinking server crashes on missing slash

4. Consider this Flask code:

@app.route('/contact')
def contact():
    return 'Contact page'

What happens if a user visits /contact/ with a trailing slash?

medium

A. Flask returns a 404 Not Found error.

B. Flask throws a server error.

C. Flask serves the page normally.

D. Flask redirects to /contact without slash.

Solution

1. Step 1: Identify route without trailing slash

   The route '/contact' is defined without a trailing slash.

2. Step 2: Check Flask behavior on extra trailing slash

   Flask does NOT redirect URLs with an extra trailing slash to the no-slash route; it returns a 404 error.

3. Final Answer:

   Flask returns a 404 Not Found error. -> Option A

4. Quick Check:

   No trailing slash route rejects extra slash URL [OK]

Hint: No trailing slash route rejects URLs with slash [OK]

Common Mistakes:

• Thinking Flask redirects to no-slash URL
• Assuming page loads normally with slash
• Believing server throws error instead of 404

5. You want a single Flask route to accept both /blog and /blog/ URLs without redirecting or 404 errors. Which approach achieves this?

hard

A. Use Flask's strict_slashes=False option on the route decorator.

B. Define one route with trailing slash: @app.route('/blog/') only.

C. Define one route without trailing slash: @app.route('/blog') only.

D. Define two routes: @app.route('/blog') and @app.route('/blog/') pointing to the same function.

Solution

1. Step 1: Understand default Flask behavior

   By default, Flask treats routes with and without trailing slash differently, redirecting or 404ing as needed.

2. Step 2: Use strict_slashes=False to accept both

   Setting strict_slashes=False on the route decorator disables strict trailing slash matching, allowing both URLs without redirect or error.

3. Final Answer:

   Use Flask's strict_slashes=False option on the route decorator. -> Option A

4. Quick Check:

   strict_slashes=False allows both URLs [OK]

Hint: Use strict_slashes=False to accept both slash and no-slash URLs [OK]

Common Mistakes:

• Defining two routes duplicates code
• Relying on default redirect behavior
• Ignoring strict_slashes option