Trailing slash behavior in Flask - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What happens when accessing a Flask route with a trailing slash?

Consider the following Flask route:

 @app.route('/hello/')
 def hello():
   return 'Hello!'

What will happen if a user visits /hello (without the trailing slash) in their browser?

Flask

@app.route('/hello/')
def hello():
    return 'Hello!'

A Flask will serve the 'Hello!' response without redirect.

B Flask will return a 404 Not Found error.

C Flask will redirect the user to '/hello/' automatically.

D Flask will raise a runtime error due to missing slash.

💡 Hint

Think about how Flask handles routes ending with a slash versus those without.

When a route is defined with a trailing slash, Flask treats it as a directory. Accessing the same route without the slash causes Flask to redirect to the slash version automatically.

❓ component_behavior

intermediate

What is the behavior of a Flask route without a trailing slash when accessed with one?

Given this Flask route:

 @app.route('/about')
 def about():
   return 'About page'

What happens if a user visits /about/ (with a trailing slash)?

Flask

@app.route('/about')
def about():
    return 'About page'

A Flask will return a 404 Not Found error.

B Flask will redirect the user to '/about' (without slash).

C Flask will raise a runtime error due to extra slash.

D Flask will serve the 'About page' response without redirect.

💡 Hint

Consider how Flask treats routes defined without trailing slashes.

When a route is defined without a trailing slash, Flask expects the URL exactly as defined. Accessing it with a trailing slash causes Flask to redirect to the no-slash version automatically.

📝 Syntax

advanced

Which Flask route definition causes a syntax error?

Identify the option that will cause a syntax error when defining a Flask route:

A

@app.route('/profile/'
def profile():
    return 'Profile'

B

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

C

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

D

@app.route('/dashboard/')
def dashboard():
    return 'Dashboard'

💡 Hint

Check for missing or mismatched parentheses in the route decorator.

Option A is missing a closing parenthesis in the @app.route decorator, causing a syntax error.

❓ state_output

advanced

What is the output when accessing a Flask route with and without trailing slash?

Given this Flask app code:

 @app.route('/item')
 def item():
   return 'Item without slash'

 @app.route('/item/')
 def item_slash():
   return 'Item with slash'

What will be the output when visiting /item and /item/ respectively?

Flask

@app.route('/item')
def item():
    return 'Item without slash'

@app.route('/item/')
def item_slash():
    return 'Item with slash'

A Visiting '/item' returns 'Item without slash'; visiting '/item/' returns 'Item with slash'.

B Both URLs return 'Item without slash'.

C Both URLs return 'Item with slash'.

D Visiting '/item' redirects to '/item/' and returns 'Item with slash'.

💡 Hint

Routes are defined separately for each URL pattern.

Each route is defined explicitly. Flask matches the exact route, so '/item' and '/item/' call different functions and return different responses.

🔧 Debug

expert

Why does this Flask app cause a redirect loop?

Examine the Flask app code:

 @app.route('/loop/')
 def loop():
   return redirect('/loop')

 @app.route('/loop')
 def loop_no_slash():
   return redirect('/loop/')

What is the cause of the redirect loop when visiting '/loop/' or '/loop'?

Flask

@app.route('/loop/')
def loop():
    return redirect('/loop')

@app.route('/loop')
def loop_no_slash():
    return redirect('/loop/')

A Flask automatically resolves the loop and serves the page.

B The app raises a runtime error due to conflicting routes.

C Only '/loop/' causes a redirect loop; '/loop' works fine.

D Both routes redirect to each other endlessly causing a loop.

💡 Hint

Check what each route redirects to and if it matches the other route.

The '/loop/' route redirects to '/loop', and '/loop' redirects back to '/loop/'. This causes an infinite redirect loop between the two URLs.