Serving sensor data as JSON API in Raspberry Pi - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import the Flask module.

Raspberry Pi

from [1] import Flask

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

AFlask

Bflask

Cjson

Drequests

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'Flask' instead of 'flask' as module name.

The Flask module is imported using from flask import Flask.

2fill in blank

medium

Complete the code to create a Flask app instance.

Raspberry Pi

app = [1](__name__)

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

AFlask

Bapp

Cflask

Djsonify

Attempts:

3 left

💡 Hint

Common Mistakes

Using lowercase 'flask' instead of 'Flask'.

The Flask app instance is created by calling Flask(__name__).

3fill in blank

hard

Fix the error in the route decorator to serve sensor data at '/sensor'.

Raspberry Pi

@app.route('[1]')
def sensor_data():
    return {'temperature': 22.5, 'humidity': 60}

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

A/sensor

B/Sensor

Csensor

D/data

Attempts:

3 left

💡 Hint

Common Mistakes

Omitting the leading slash.

Using uppercase letters in the path.

The route must start with a slash and match the URL path exactly, so '/sensor' is correct.

4fill in blank

hard

Fill both blanks to return JSON response using Flask's jsonify function.

Raspberry Pi

from flask import Flask, [1]

@app.route('/sensor')
def sensor_data():
    data = {'temperature': 22.5, 'humidity': 60}
    return [2](data)

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

Ajsonify

Bjson

CFlask

Drequest

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'json' instead of 'jsonify'.

Not importing jsonify.

The jsonify function is imported and used to return JSON responses in Flask.

5fill in blank

hard

Fill all three blanks to run the Flask app on host '0.0.0.0' and port 5000.

Raspberry Pi

if __name__ == '__main__':
    app.run(host=[1], port=[2], debug=[3])

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

A'127.0.0.1'

B5000

CTrue

D'0.0.0.0'

Attempts:

3 left

💡 Hint

Common Mistakes

Using '127.0.0.1' limits access to localhost only.

Setting debug to False during development.

To make the Flask app accessible on the network, use host '0.0.0.0', port 5000, and enable debug mode with True.

Practice

1.

What is the main purpose of serving sensor data as a JSON API on a Raspberry Pi?

easy

A. To allow other devices to easily access sensor information in a standard format

B. To store sensor data only on the Raspberry Pi without sharing

C. To convert sensor data into images for display

D. To run heavy calculations on sensor data locally

Solution

1. Step 1: Understand JSON API purpose

   A JSON API provides data in a simple, standard format that other devices can read easily.

2. Step 2: Relate to sensor data sharing

   Serving sensor data as JSON means sharing sensor readings so other devices or apps can use them.

3. Final Answer:

   To allow other devices to easily access sensor information in a standard format -> Option A

4. Quick Check:

   JSON API shares sensor data easily [OK]

Hint: JSON API means sharing data in a simple format [OK]

Common Mistakes:

• Thinking JSON API stores data only locally
• Confusing JSON API with image or video output
• Assuming JSON API does heavy local processing

2.

Which of the following is the correct way to import Flask in a Python script on Raspberry Pi?

?

easy

A. import flask

B. import Flask

C. from Flask import flask

D. from flask import Flask

Solution

1. Step 1: Recall Flask import syntax

   The Flask class is imported from the flask module using: from flask import Flask

2. Step 2: Check options for correct case and syntax

   from flask import Flask matches correct syntax and case; others have wrong case or structure.

3. Final Answer:

   from flask import Flask -> Option D

4. Quick Check:

   Correct Flask import uses 'from flask import Flask' [OK]

Hint: Flask class is imported with 'from flask import Flask' [OK]

Common Mistakes:

• Using wrong capitalization like 'import Flask'
• Importing the whole module without accessing Flask class
• Mixing module and class names incorrectly

3.

What will be the output of this Flask route when accessed?

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

@app.route('/sensor')
def sensor_data():
    data = {'temperature': 22.5, 'humidity': 60}
    return jsonify(data)

# Assume app is running

medium

A. Error: jsonify not defined

B. {temperature: 22.5, humidity: 60}

C. {"temperature": 22.5, "humidity": 60}

D. ['temperature', 22.5, 'humidity', 60]

Solution

1. Step 1: Understand jsonify output

   jsonify converts Python dict to JSON string with keys in quotes and proper JSON format.

2. Step 2: Match output format

   {"temperature": 22.5, "humidity": 60} shows correct JSON string with keys and values properly formatted.

3. Final Answer:

   {"temperature": 22.5, "humidity": 60} -> Option C

4. Quick Check:

   jsonify returns JSON string with quoted keys [OK]

Hint: jsonify outputs JSON with quoted keys and values [OK]

Common Mistakes:

• Forgetting quotes around keys in JSON output
• Confusing Python dict print with JSON string
• Assuming jsonify returns Python list

4.

Identify the error in this Flask code snippet that serves sensor data as JSON:

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

@app.route('/data')
def data():
    sensor = {'temp': 25}
    return json.dumps(sensor)

app.run()

medium

A. json.dumps is used instead of jsonify

B. Flask app is not created correctly

C. Route decorator syntax is wrong

D. Missing import for Flask

Solution

1. Step 1: Check JSON response method

   Flask expects jsonify to create proper response with correct headers, not json.dumps.

2. Step 2: Identify error cause

   Using json.dumps returns a string without correct content-type, causing client issues.

3. Final Answer:

   json.dumps is used instead of jsonify -> Option A

4. Quick Check:

   Use jsonify, not json.dumps, for Flask JSON responses [OK]

Hint: Use jsonify for Flask JSON responses, not json.dumps [OK]

Common Mistakes:

• Returning json.dumps output directly in Flask
• Not importing jsonify
• Assuming json.dumps sets response headers

5.

You want to serve live temperature sensor data from a Raspberry Pi using Flask. Which approach correctly updates the JSON response with real sensor readings each time the API is called?

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

def read_temp_sensor():
    # Returns current temperature reading
    return 24.7

@app.route('/temp')
def temp():
    # Fill in here

app.run()

hard

A. temp = 24.7
return jsonify({'temperature': temp})

B. temp = read_temp_sensor()
return jsonify({'temperature': temp})

C. return jsonify({'temperature': read_temp_sensor})

D. return {'temperature': read_temp_sensor()} # Flask auto converts

Solution

1. Step 1: Call sensor function inside route

   We must call read_temp_sensor() to get current value each time the route is accessed.

2. Step 2: Return JSON response with current value

   Assign the value to a variable and pass it to jsonify to return proper JSON response.

3. Final Answer:

   temp = read_temp_sensor() return jsonify({'temperature': temp}) -> Option B

4. Quick Check:

   Call sensor function and jsonify result each request [OK]

Hint: Call sensor function inside route, then jsonify result [OK]

Common Mistakes:

• Returning function object instead of calling it
• Using fixed value instead of live sensor reading
• Returning dict without jsonify in Flask