Route with dynamic parameters in Flask - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What is the output when accessing /user/42?

Given the Flask route below, what will be the response text when a client visits /user/42?

Flask

from flask import Flask
app = Flask(__name__)

@app.route('/user/<int:user_id>')
def show_user(user_id):
    return f"User ID is {user_id}"

A User ID is 42

B User ID is <int:user_id>

C User ID is user_id

D 404 Not Found

💡 Hint

Look at how the route captures the integer parameter and uses it in the function.

The route uses <int:user_id> to capture an integer from the URL and passes it as an argument to the function. The function returns a string with that integer included.

📝 Syntax

intermediate

Which route definition correctly captures a string username?

Select the correct Flask route decorator to capture a string username from the URL path /profile/<username>.

A @app.route('/profile/<int:username>')

B @app.route('/profile/<path:username>')

C @app.route('/profile/<float:username>')

D @app.route('/profile/<username>')

💡 Hint

The default converter for dynamic parts is string.

Using <username> captures a string by default. The other converters expect specific types like int or float.

🔧 Debug

advanced

Why does this route cause a 404 error for /item/abc123?

Examine the Flask route below. Why does visiting /item/abc123 return a 404 error?

Flask

from flask import Flask
app = Flask(__name__)

@app.route('/item/<int:item_id>')
def get_item(item_id):
    return f"Item {item_id}"

A The function get_item is missing a return statement.

B The route expects an integer, but 'abc123' is not an integer, so no match is found.

C Flask routes cannot have dynamic parameters.

D The route should use <string:item_id> instead of <int:item_id>.

💡 Hint

Check the type converter in the route and the URL parameter.

The route uses <int:item_id>, so Flask only matches URLs where the part after /item/ is an integer. 'abc123' is not an integer, so Flask returns 404.

❓ state_output

advanced

What is the output of this route with multiple parameters?

Given the Flask route below, what is the response when visiting /order/7/item/3?

Flask

from flask import Flask
app = Flask(__name__)

@app.route('/order/<int:order_id>/item/<int:item_id>')
def order_item(order_id, item_id):
    return f"Order {order_id}, Item {item_id}"

A Order order_id, Item item_id

B Order <int:order_id>, Item <int:item_id>

C Order 7, Item 3

D 404 Not Found

💡 Hint

Look at how multiple dynamic parameters are captured and used.

The route captures two integers from the URL and passes them as arguments to the function, which returns a formatted string with those values.

🧠 Conceptual

expert

What happens if two routes overlap with dynamic parameters?

Consider these two Flask routes:

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

@app.route('/page/')
def page(page_name):
    return f"Page: {page_name}"

What will be the response when visiting /page/about?

A About Page

B Page: about

C 404 Not Found

D RuntimeError due to route conflict

💡 Hint

Flask matches routes in the order they are defined and prefers exact matches over dynamic ones.

Flask matches routes in the order they are added. Since /page/about is an exact static route, it matches before the dynamic /page/<page_name> route. So the 'About Page' response is returned.