Flask web server on Raspberry Pi - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import the Flask class from the flask module.

Raspberry Pi

from flask import [1]

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

AWeb

BServer

CApp

DFlask

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect class names like Server or App instead of Flask.

The Flask class is imported from the flask module to create a web server.

2fill in blank

medium

Complete the code to create a Flask app instance named 'app'.

Raspberry Pi

app = [1](__name__)

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

AServer

BFlask

CWeb

DApp

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect class names or missing parentheses.

Creating the Flask app instance requires calling Flask with __name__ as argument.

3fill in blank

hard

Fix the error in the route decorator to define the home page route.

Raspberry Pi

@app.route('[1]')
def home():
    return 'Hello, Raspberry Pi!'

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

A/

B/home

Chome

Dindex

Attempts:

3 left

💡 Hint

Common Mistakes

Using route names without a leading slash or incorrect paths.

The home page route should be '/' to respond to the root URL.

4fill in blank

hard

Fill both blanks to run the Flask app on all network interfaces with debug mode on.

Raspberry Pi

if __name__ == '__main__':
    app.run(host=[1], debug=[2])

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

A'0.0.0.0'

BTrue

CFalse

D'localhost'

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'localhost' limits access to the Pi only.

Setting debug to False disables helpful error messages.

Using host='0.0.0.0' makes the server accessible on the local network. Setting debug=True enables debug mode.

5fill in blank

hard

Fill all three blanks to create a route '/status' that returns JSON with a message and status code 200.

Raspberry Pi

@app.route([1])
def status():
    return [2], [3]

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

A'/status'

B{'message': 'Server is running'}

C200

D'/status/'

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect route paths or returning strings instead of dictionaries.

The route '/status' returns a dictionary message and HTTP status code 200.

Practice

1. What does the @app.route decorator do in a Flask web server on Raspberry Pi?

easy

A. It installs Flask on the Raspberry Pi.

B. It starts the Flask server to listen for requests.

C. It defines the URL path that triggers a specific function.

D. It stops the Flask server from running.

Solution

1. Step 1: Understand the role of @app.route

   This decorator tells Flask which URL path should run the function below it.

2. Step 2: Connect URL to function

   When a user visits that URL, Flask runs the linked function to generate a response.

3. Final Answer:

   It defines the URL path that triggers a specific function. -> Option C

4. Quick Check:

   @app.route sets URL path [OK]

Hint: Remember: route = URL path to function [OK]

Common Mistakes:

• Thinking it starts or stops the server
• Confusing it with installing Flask
• Assuming it runs the server automatically

2. Which of the following is the correct way to run a Flask app on Raspberry Pi so it is accessible from other devices on the network?

easy

A. app.run(host='0.0.0.0')

B. app.run(host='127.0.0.1')

C. app.run()

D. app.run(port=8080)

Solution

1. Step 1: Understand host parameter in app.run()

   By default, Flask listens only on localhost (127.0.0.1), meaning only the Pi itself can access it.

2. Step 2: Use host='0.0.0.0' to allow network access

   Setting host to '0.0.0.0' tells Flask to listen on all network interfaces, so other devices can connect.

3. Final Answer:

   app.run(host='0.0.0.0') -> Option A

4. Quick Check:

   host='0.0.0.0' allows network access [OK]

Hint: Use host='0.0.0.0' to share server on network [OK]

Common Mistakes:

• Using default host which blocks external access
• Confusing port with host
• Using localhost IP which restricts access

3. What will be the output when you visit http://raspberrypi.local/hello given this Flask code on Raspberry Pi?

from flask import Flask
app = Flask(__name__)

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

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

medium

A. Server does not start

B. 404 Not Found error

C. SyntaxError

D. Hello, Raspberry Pi!

Solution

1. Step 1: Check the route and function

   The route '/hello' is defined and returns the string 'Hello, Raspberry Pi!'.

2. Step 2: Accessing the URL

   Visiting /hello triggers the function and returns the string as the web page content.

3. Final Answer:

   Hello, Raspberry Pi! -> Option D

4. Quick Check:

   Route '/hello' returns greeting string [OK]

Hint: Match URL path to function return value [OK]

Common Mistakes:

• Expecting a 404 error if route is correct
• Thinking code has syntax errors
• Assuming server won't start with host='0.0.0.0'

4. Identify the error in this Flask code snippet intended to run on Raspberry Pi:

from flask import Flask
app = Flask(__name__)

@app.route('/status')
def status():
print('Server is running')

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

medium

A. Incorrect host value in app.run().

B. Missing indentation for the print statement inside the function.

C. Missing import statement for Flask.

D. Route decorator syntax is wrong.

Solution

1. Step 1: Check function body indentation

   The print statement inside the function must be indented to be part of the function block.

2. Step 2: Verify other parts

   Host value '0.0.0.0' is correct, Flask is imported, and route syntax is valid.

3. Final Answer:

   Missing indentation for the print statement inside the function. -> Option B

4. Quick Check:

   Python requires indentation inside functions [OK]

Hint: Indent function code properly in Python [OK]

Common Mistakes:

• Ignoring indentation errors
• Changing host unnecessarily
• Misreading route decorator syntax

5. You want your Flask app on Raspberry Pi to show different messages at / and /info. Which code correctly sets up these two routes?

hard

A. from flask import Flask
app = Flask(__name__)

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

@app.route('/info')
def info():
return 'Raspberry Pi Info'

app.run(host='0.0.0.0')

B. from flask import Flask
app = Flask(__name__)

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

@app.route('/')
def info():
return 'Raspberry Pi Info'

app.run(host='0.0.0.0')

C. from flask import Flask
app = Flask(__name__)

@app.route('/info')
def home():
return 'Welcome!'

@app.route('/')
def info():
return 'Raspberry Pi Info'

app.run(host='0.0.0.0')

D. from flask import Flask
app = Flask(__name__)

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

@app.route('/info')
def info():
return 'Raspberry Pi Info'

app.run(host='0.0.0.0')

Solution

1. Step 1: Check route paths and functions

   from flask import Flask app = Flask(__name__) @app.route('/') def home(): return 'Welcome!' @app.route('/info') def info(): return 'Raspberry Pi Info' app.run(host='0.0.0.0') correctly uses '/' for home and '/info' for info, each with its own function returning the right message.

2. Step 2: Verify no route conflicts

   from flask import Flask app = Flask(__name__) @app.route('/') def home(): return 'Welcome!' @app.route('/') def info(): return 'Raspberry Pi Info' app.run(host='0.0.0.0') uses '/' twice, which causes conflict. from flask import Flask app = Flask(__name__) @app.route('/info') def home(): return 'Welcome!' @app.route('/') def info(): return 'Raspberry Pi Info' app.run(host='0.0.0.0') swaps routes and functions incorrectly. from flask import Flask app = Flask(__name__) @app.route('/home') def home(): return 'Welcome!' @app.route('/info') def info(): return 'Raspberry Pi Info' app.run(host='0.0.0.0') uses '/home' instead of '/'.

3. Final Answer:

   Option A correctly defines two distinct routes '/' and '/info'. -> Option A

4. Quick Check:

   Unique routes need unique paths [OK]

Hint: Use unique URLs for each route function [OK]

Common Mistakes:

• Defining two functions for the same route
• Swapping route paths and function names
• Using wrong URL paths like '/home' instead of '/'