Flask web server on Raspberry Pi - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Flask route response output

What is the output when you visit the root URL '/' of this Flask app running on Raspberry Pi?

Raspberry Pi

from flask import Flask
app = Flask(__name__)

@app.route('/')
def home():
    return 'Hello from Raspberry Pi!'

if __name__ == '__main__':
    app.run(host='0.0.0.0', port=5000)

A Hello World!

B Hello from Raspberry Pi!

C 500 Internal Server Error

D 404 Not Found

💡 Hint

Look at the return value of the home() function.

The route '/' returns the string 'Hello from Raspberry Pi!'. Visiting this URL shows that exact text.

🧠 Conceptual

intermediate

Purpose of host='0.0.0.0' in Flask app

Why do we use host='0.0.0.0' when running a Flask app on Raspberry Pi?

A To allow the Flask app to accept connections from any device on the network

B To restrict the Flask app to only accept connections from localhost

C To enable HTTPS encryption automatically

D To run the Flask app on a random port

💡 Hint

Think about network accessibility from other devices.

Setting host='0.0.0.0' makes the Flask server listen on all network interfaces, allowing other devices to connect.

🔧 Debug

advanced

Identify the error in this Flask app code

What error will this Flask app code produce when run on Raspberry Pi?

Raspberry Pi

from flask import Flask
app = Flask(__name__)

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

if __name__ == '__main__':
    app.run(host='0.0.0.0')

A IndentationError: expected an indented block

B TypeError: app.route() missing required positional argument

C NameError: name 'app' is not defined

D No error, runs fine

💡 Hint

Check the indentation of the function body.

The function hello() has no indentation for its return statement, causing an IndentationError.

❓ Predict Output

advanced

Flask app with dynamic URL parameter output

What is the output when visiting '/user/Alice' on this Flask app running on Raspberry Pi?

Raspberry Pi

from flask import Flask
app = Flask(__name__)

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

if __name__ == '__main__':
    app.run(host='0.0.0.0')

A 404 Not Found

B User: <name>

C User: Alice

D User: user

💡 Hint

Look at how the URL parameter is used in the return string.

The route captures the name from the URL and returns it in the string 'User: {name}'.

📝 Syntax

expert

Identify the syntax error in this Flask app snippet

Which option correctly identifies the syntax error in this Flask app code snippet?

Raspberry Pi

from flask import Flask
app = Flask(__name__)

@app.route('/data')
def data():
    return {'value': 42}

if __name__ == '__main__':
    app.run(host='0.0.0.0')

A Flask app must import jsonify to return JSON data

B Missing colon after the function definition line

C app.run() missing required port argument

D Returning a dictionary directly causes a TypeError because Flask expects a string or Response object

💡 Hint

Think about what Flask accepts as a return value from route functions.

Returning a plain dictionary causes a TypeError because Flask cannot convert it automatically to a response.