Why APIs matter in Flask - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a basic Flask API endpoint that returns a greeting message.

Flask

from flask import Flask
app = Flask(__name__)

@app.route('/hello')
def hello():
    return [1]

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

A"Hello, API!"

Bprint("Hello, API!")

Creturn Hello, API!

Dresponse("Hello, API!")

Attempts:

3 left

💡 Hint

Common Mistakes

Using print instead of return

Not using quotes around the string

The function must return a string as the response. Using quotes around the string is required.

2fill in blank

medium

Complete the code to import the Flask class correctly.

Flask

[1] Flask
app = Flask(__name__)

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

Afrom flask import

Bfrom flask

Cimport

Dinclude

Attempts:

3 left

💡 Hint

Common Mistakes

Using only 'import flask'

Using 'include' which is not Python syntax

To use Flask, you import the Flask class from the flask module using 'from flask import Flask'.

3fill in blank

hard

Fix the error in the route decorator to correctly define the API endpoint.

Flask

@app.route([1])
def greet():
    return "Hi there!"

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

Agreet

B/greet

C'/greet'

D"greet"

Attempts:

3 left

💡 Hint

Common Mistakes

Missing quotes around the path

Not starting the path with a slash

The route path must be a string with quotes, starting with a slash.

4fill in blank

hard

Fill both blanks to create a JSON response from the API using Flask's jsonify.

Flask

from flask import Flask, [1]

app = Flask(__name__)

@app.route('/data')
def data():
    return [2]({'message': 'Hello, JSON!'})

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

Ajsonify

Bjson

Cmake_response

DResponse

Attempts:

3 left

💡 Hint

Common Mistakes

Importing json instead of jsonify

Using make_response without jsonify

Flask's jsonify function is imported and used to return JSON responses easily.

5fill in blank

hard

Fill all three blanks to create a Flask API that accepts a POST request and returns the posted JSON data.

Flask

from flask import Flask, request, jsonify

app = Flask(__name__)

@app.route('/postdata', methods=[[1]])
def post_data():
    data = request.[2]
    return jsonify([3])

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

A"POST"

Bjson

Cdata

DGET

Attempts:

3 left

💡 Hint

Common Mistakes

Using GET instead of POST

Accessing request.data instead of request.json

Returning raw data without jsonify

The route must allow POST method, access JSON data from request.json, and return it with jsonify.

Practice

1. Why are APIs important when building web applications with Flask?

easy

A. They automatically create user interfaces.

B. They allow different apps to share data and features easily.

C. They make the app run faster on the server.

D. They replace the need for a database.

Solution

1. Step 1: Understand the role of APIs in app communication

   APIs let different software talk to each other by sharing data and features.

2. Step 2: Relate this to Flask's use of APIs

   Flask helps build APIs that send and receive data, enabling app interaction.

3. Final Answer:

   They allow different apps to share data and features easily. -> Option B

4. Quick Check:

   APIs enable app communication = C [OK]

Hint: APIs connect apps by sharing data and features [OK]

Common Mistakes:

• Thinking APIs speed up server processing
• Believing APIs create user interfaces automatically
• Assuming APIs replace databases

2. Which Flask code snippet correctly defines a simple API route that returns JSON data?

easy

A. @app.route('/data')\ndef get_data():\n return {'key': 'value'}

B. app.route('/data')\ndef get_data():\n return {'key': 'value'}

C. @app.route('/data')\ndef get_data():\n print({'key': 'value'})

D. app.route('/data')\ndef get_data():\n print({'key': 'value'})

Solution

1. Step 1: Identify correct Flask route decorator syntax

   Flask routes require the '@app.route' decorator before the function.

2. Step 2: Check the function returns JSON data properly

   The function should return a dictionary (Flask converts it to JSON), not print it.

3. Final Answer:

   @app.route('/data')\ndef get_data():\n return {'key': 'value'} -> Option A

4. Quick Check:

   Correct decorator and return = B [OK]

Hint: Use @app.route and return data, not print [OK]

Common Mistakes:

• Missing '@' before app.route
• Using print instead of return
• Not returning data from the function

3. What will be the output when accessing the Flask API route defined below?

@app.route('/hello')
def hello():
    return {'message': 'Hi there!'}

medium

A. A server error because return type is wrong

B. A plain text response: Hi there!

C. A JSON response: {"message": "Hi there!"}

D. An HTML page with the text 'Hi there!'

Solution

1. Step 1: Understand Flask's automatic JSON conversion

   Returning a dictionary from a route makes Flask send JSON response automatically.

2. Step 2: Check the returned dictionary content

   The dictionary has key 'message' with value 'Hi there!', so JSON will reflect that.

3. Final Answer:

   A JSON response: {"message": "Hi there!"} -> Option C

4. Quick Check:

   Return dict = JSON response = A [OK]

Hint: Return dict from route to get JSON response [OK]

Common Mistakes:

• Expecting plain text instead of JSON
• Thinking Flask returns HTML automatically
• Assuming a server error from dict return

4. Identify the error in this Flask API code snippet:

@app.route('/data', methods=['POST'])
def data():
    data = request.get_json
    return {'received': data}

medium

A. Flask routes cannot accept JSON data.

B. The route should use GET method instead of POST.

C. The return statement should use print instead of return.

D. request.get_json() is missing parentheses, so data is a method, not JSON.

Solution

1. Step 1: Check how request.get_json is used

   request.get_json is a method and must be called with parentheses to get JSON data.

2. Step 2: Understand the impact of missing parentheses

   Without (), data is a method object, not the JSON content, causing wrong output.

3. Final Answer:

   request.get_json() is missing parentheses, so data is a method, not JSON. -> Option D

4. Quick Check:

   Call get_json() method properly = D [OK]

Hint: Always call get_json() with parentheses [OK]

Common Mistakes:

• Forgetting parentheses on get_json
• Using wrong HTTP method for route
• Using print instead of return in route

5. You want to create a Flask API that accepts a POST request with JSON containing a user's name and returns a greeting. Which code correctly implements this?

hard

A. @app.route('/greet', methods=['POST'])\ndef greet():\n data = request.get_json()\n name = data.get('name', 'Guest')\n return {'greeting': f'Hello, {name}!'}

B. @app.route('/greet')\ndef greet():\n name = request.args.get('name')\n return {'greeting': f'Hello, {name}!'}

C. @app.route('/greet', methods=['GET'])\ndef greet():\n data = request.get_json()\n return {'greeting': 'Hello!'}

D. @app.route('/greet', methods=['POST'])\ndef greet():\n name = request.form['name']\n return {'greeting': f'Hello, {name}!'}

Solution

1. Step 1: Check the HTTP method and route setup

   The API must accept POST requests, so methods=['POST'] is correct.

2. Step 2: Verify JSON data extraction and greeting creation

   Using request.get_json() gets JSON data; then safely get 'name' with default 'Guest'.

3. Step 3: Confirm the returned JSON greeting format

   Return a dictionary with the greeting message using an f-string for the name.

4. Final Answer:

   Correct POST route with JSON input and greeting response. -> Option A

5. Quick Check:

   POST + get_json() + return greeting = A [OK]

Hint: Use POST method and request.get_json() to read JSON data [OK]

Common Mistakes:

• Using GET instead of POST for JSON input
• Trying to get JSON data from request.args or form
• Not handling missing 'name' key safely