API key authentication concept in Flask - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import the Flask class.

Flask

from flask import [1]

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

AFlask

BRequest

Cjsonify

DBlueprint

Attempts:

3 left

💡 Hint

Common Mistakes

Importing Request instead of Flask

Using lowercase flask instead of Flask

The Flask class is imported from the flask module to create the app.

2fill in blank

medium

Complete the code to get the API key from request headers.

Flask

api_key = request.headers.get('[1]')

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

AAuthorization

BX-API-KEY

CContent-Type

DUser-Agent

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'Authorization' header instead

Using 'Content-Type' header

The API key is usually sent in a custom header like 'X-API-KEY'.

3fill in blank

hard

Fix the error in the code to check if the API key matches the expected key.

Flask

if api_key != [1]:
    return {'error': 'Unauthorized'}, 401

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

Aapi_key

Bmysecretkey

CNone

D'mysecretkey'

Attempts:

3 left

💡 Hint

Common Mistakes

Not using quotes around the key

Comparing api_key to itself

The expected API key should be a string literal in quotes.

4fill in blank

hard

Fill both blanks to create a Flask route that requires API key authentication.

Flask

@app.route('/data', methods=[[1]])
def get_data():
    api_key = request.headers.get('X-API-KEY')
    if api_key != 'mysecretkey':
        return [2], 401
    return {'data': 'Here is your data'}

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

A'GET'

B{'error': 'Unauthorized'}

C'POST'

D{'message': 'Success'}

Attempts:

3 left

💡 Hint

Common Mistakes

Using POST instead of GET

Returning success message on unauthorized

The route should accept GET requests and return an error dictionary with 401 if unauthorized.

5fill in blank

hard

Fill all three blanks to complete the Flask app with API key check and run the server.

Flask

from flask import Flask, request

app = Flask(__name__)

@app.route('/info', methods=[[1]])
def info():
    key = request.headers.get('X-API-KEY')
    if key != [2]:
        return [3], 401
    return {'info': 'Secret info'}

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

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

A'GET'

B'supersecret'

C{'error': 'Unauthorized'}

D'POST'

Attempts:

3 left

💡 Hint

Common Mistakes

Using POST method

Not quoting the API key

Returning success on wrong key

The route uses GET method, checks the API key string 'supersecret', and returns an error dictionary with 401 if unauthorized.

Practice

1. What is the main purpose of using an API key in Flask applications?

easy

A. To style the API output

B. To verify that the client is authorized to access the API

C. To speed up the API response time

D. To store user passwords securely

Solution

1. Step 1: Understand API key role

   An API key is a secret token sent by the client to prove identity.

2. Step 2: Identify purpose in Flask

   The server checks this key to allow or deny access to API resources.

3. Final Answer:

   To verify that the client is authorized to access the API -> Option B

4. Quick Check:

   API key = Authorization [OK]

Hint: API keys prove client identity to server [OK]

Common Mistakes:

• Thinking API keys speed up responses
• Confusing API keys with styling tools
• Using API keys to store passwords

2. Which of the following is the correct way to retrieve an API key from request headers in Flask?

easy

A. api_key = request.cookies.get('X-API-KEY')

B. api_key = request.args['X-API-KEY']

C. api_key = request.form['X-API-KEY']

D. api_key = request.headers.get('X-API-KEY')

Solution

1. Step 1: Identify where API keys are usually sent

   API keys are commonly sent in HTTP headers for security.

2. Step 2: Use Flask syntax to get header value

   Use request.headers.get('Header-Name') to safely retrieve header values.

3. Final Answer:

   api_key = request.headers.get('X-API-KEY') -> Option D

4. Quick Check:

   Headers use request.headers.get() [OK]

Hint: Use request.headers.get() for header values [OK]

Common Mistakes:

• Using request.args for headers
• Trying to get API key from form data
• Looking for API key in cookies

3. Given this Flask code snippet, what will be the response if the client sends a request with header X-API-KEY: wrongkey?

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

VALID_API_KEY = 'secret123'

@app.route('/data')
def data():
    api_key = request.headers.get('X-API-KEY')
    if api_key == VALID_API_KEY:
        return jsonify({'message': 'Access granted'})
    else:
        return jsonify({'error': 'Unauthorized'}), 401

medium

A. {"error": "Unauthorized"}

B. {"message": "Access granted"}

C. 500 Internal Server Error

D. Empty response with status 200

Solution

1. Step 1: Check API key comparison

   The code compares the header key to 'secret123'. 'wrongkey' does not match.

2. Step 2: Determine response for wrong key

   Since keys differ, the else block returns a JSON error with status 401.

3. Final Answer:

   {"error": "Unauthorized"} -> Option A

4. Quick Check:

   Wrong key = Unauthorized error [OK]

Hint: Wrong key triggers 401 Unauthorized JSON error [OK]

Common Mistakes:

• Assuming any key grants access
• Expecting 500 error for wrong key
• Thinking response is empty

4. Identify the error in this Flask API key check code:

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

VALID_KEY = 'abc123'

@app.route('/info')
def info():
    api_key = request.headers['X-API-KEY']
    if api_key = VALID_KEY:
        return 'Access allowed'
    else:
        return 'Access denied', 403

medium

A. Using single equals (=) instead of double equals (==) in if condition

B. Accessing headers with request.headers.get() instead of []

C. Missing return type for response

D. Route decorator syntax is incorrect

Solution

1. Step 1: Check if condition syntax

   The if statement uses '=' which is assignment, not comparison.

2. Step 2: Correct comparison operator

   Use '==' to compare api_key and VALID_KEY for equality check.

3. Final Answer:

   Using single equals (=) instead of double equals (==) in if condition -> Option A

4. Quick Check:

   Comparison needs '==' not '=' [OK]

Hint: Use '==' for comparison, '=' is assignment [OK]

Common Mistakes:

• Confusing '=' with '==' in conditions
• Thinking request.headers['X-API-KEY'] is wrong
• Believing return type must be explicit

5. You want to protect multiple Flask routes using the same API key check without repeating code. Which approach is best to implement this efficiently?

hard

A. Copy the API key check code inside every route function

B. Check the API key only in the first route and assume others are safe

C. Create a decorator function that checks the API key before running the route function

D. Use a global variable to store the API key and skip checks

Solution

1. Step 1: Understand code reuse for API key checks

   Repeating code in every route is inefficient and error-prone.

2. Step 2: Use a decorator to wrap routes

   A decorator can run the API key check before the route logic, applying it to many routes cleanly.

3. Final Answer:

   Create a decorator function that checks the API key before running the route function -> Option C

4. Quick Check:

   Decorator = reusable API key check [OK]

Hint: Use decorators to avoid repeating API key checks [OK]

Common Mistakes:

• Copy-pasting code in every route
• Skipping checks on some routes
• Using global variables to bypass security