How Flask processes HTTP requests - Practice Exercises

Challenge - 5 Problems

❓ component_behavior

intermediate

What does this Flask route return?

Consider this Flask app code. What is the output when you visit /hello in a browser?

Flask

from flask import Flask
app = Flask(__name__)

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

if __name__ == '__main__':
    app.run()

A The browser shows a blank page

B The browser shows a 404 Not Found error

C The browser shows a 500 Internal Server Error

D The browser shows the text: Hello, Flask!

💡 Hint

Check the route decorator and the return value of the function.

The route decorator @app.route('/hello') connects the URL path '/hello' to the hello() function. When you visit '/hello', Flask calls hello() and returns its string, which the browser displays.

❓ state_output

intermediate

What is the value of request.method inside this route?

Given this Flask route, what will request.method be if you send a POST request to /submit?

Flask

from flask import Flask, request
app = Flask(__name__)

@app.route('/submit', methods=['GET', 'POST'])
def submit():
    return f'Method used: {request.method}'

if __name__ == '__main__':
    app.run()

A PUT

B GET

C POST

D DELETE

💡 Hint

Look at the HTTP method used in the request and the allowed methods in the route.

The route allows GET and POST. If you send a POST request, request.method will be 'POST'.

📝 Syntax

advanced

Which option correctly defines a Flask route that accepts a dynamic integer parameter?

You want a route that matches URLs like /user/42 where 42 is a number. Which code snippet correctly defines this route?

A

@app.route('/user/<id:int>')
def user(id):
    return f'User {id}'

B

@app.route('/user/<int:id>')
def user(id):
    return f'User {id}'

C

@app.route('/user/<int>')
def user(id):
    return f'User {id}'

D

@app.route('/user/<id>')
def user(int):
    return f'User {int}'

💡 Hint

Flask uses syntax for dynamic parts in routes.

Flask route parameters use syntax. means convert the URL part to int and assign to id.

🔧 Debug

advanced

Why does this Flask app raise a RuntimeError?

This Flask app code raises a RuntimeError: Working outside of application context. Why?

Flask

from flask import Flask, current_app
app = Flask(__name__)

print(current_app.name)

if __name__ == '__main__':
    app.run()

A Because current_app is accessed outside a request or app context

B Because Flask app is not created correctly

C Because print statement is inside the if __name__ == '__main__' block

D Because app.run() is missing parentheses

💡 Hint

current_app needs an active application context to work.

current_app only works inside an application context, which Flask creates during requests or when pushed manually. Accessing it at the top level causes RuntimeError.

🧠 Conceptual

expert

What is the correct order Flask processes an incoming HTTP request?

Arrange these steps in the order Flask processes an HTTP request internally.

A 2,1,3,4

B 1,2,3,4

C 2,3,1,4

D 1,3,2,4

💡 Hint

Flask needs a context before matching routes and running code.

Flask first creates a request context, then matches the URL to a route, runs the route function, then sends the response.