API versioning with blueprints in Flask - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What is the output of this Flask route versioning setup?

Given two blueprints registered with different URL prefixes for API versions, what URL will respond with 'Hello from v1'?

Flask

from flask import Flask, Blueprint

app = Flask(__name__)

v1 = Blueprint('v1', __name__, url_prefix='/api/v1')

@v1.route('/hello')
def hello_v1():
    return 'Hello from v1'

v2 = Blueprint('v2', __name__, url_prefix='/api/v2')

@v2.route('/hello')
def hello_v2():
    return 'Hello from v2'

app.register_blueprint(v1)
app.register_blueprint(v2)

A GET request to /hello returns 'Hello from v1'

B GET request to /api/v1/hello returns 'Hello from v1'

C GET request to /api/hello returns 'Hello from v1'

D GET request to /api/v2/hello returns 'Hello from v1'

💡 Hint

Think about how the url_prefix affects the route URL.

The blueprint v1 is registered with prefix /api/v1. So the route /hello inside it becomes /api/v1/hello. Only option B matches this.

📝 Syntax

intermediate

Which option correctly registers two versioned blueprints in Flask?

Choose the code snippet that correctly registers two blueprints v1 and v2 with URL prefixes /api/v1 and /api/v2 respectively.

A

app.register_blueprint(v1)
app.register_blueprint(v2)

v1.url_prefix = '/api/v1'
v2.url_prefix = '/api/v2'

B

app.register_blueprint(v1, url_prefix='/api/v1')
app.register_blueprint(v2, url_prefix='/api/v2')

C

v1 = Blueprint('v1', __name__)
v2 = Blueprint('v2', __name__)
app.register_blueprint(v1, url_prefix='/api/v1')
app.register_blueprint(v2, url_prefix='/api/v2')

D

v1 = Blueprint('v1', __name__, url_prefix='/api/v1')
v2 = Blueprint('v2', __name__, url_prefix='/api/v2')
app.register_blueprint(v1)
app.register_blueprint(v2)

💡 Hint

Remember where the url_prefix should be set: at blueprint creation or registration.

Setting url_prefix at blueprint creation is the recommended way. Option D does this correctly. Option D sets prefixes at registration but without blueprints having no prefix, which is allowed but less common. Option D tries to set url_prefix after registration which does nothing. Option D misses prefixes at blueprint creation.

❓ state_output

advanced

What is the response when accessing an unregistered API version route?

Given blueprints registered for /api/v1 and /api/v2, what happens when a client requests /api/v3/hello?

Flask

from flask import Flask, Blueprint

app = Flask(__name__)

v1 = Blueprint('v1', __name__, url_prefix='/api/v1')
@v1.route('/hello')
def hello_v1():
    return 'Hello from v1'

v2 = Blueprint('v2', __name__, url_prefix='/api/v2')
@v2.route('/hello')
def hello_v2():
    return 'Hello from v2'

app.register_blueprint(v1)
app.register_blueprint(v2)

A 404 Not Found error

B 500 Internal Server Error

C 'Hello from v1' response

D 'Hello from v2' response

💡 Hint

Think about what happens if no route matches the requested URL.

Since no blueprint or route is registered for /api/v3/hello, Flask returns a 404 Not Found error.

🔧 Debug

advanced

Why does this Flask app return 404 for /api/v1/hello despite blueprint registration?

Consider this code snippet. The route /hello is defined inside blueprint v1 with prefix /api/v1. But accessing /api/v1/hello returns 404. What is the likely cause?

Flask

from flask import Flask, Blueprint

app = Flask(__name__)

v1 = Blueprint('v1', __name__, url_prefix='/api/v1')

@app.route('/hello')
def hello():
    return 'Hello from v1'

app.register_blueprint(v1)

A The route is registered on app, not on blueprint v1

B The blueprint url_prefix is incorrect

C The blueprint was not registered

D The route function name conflicts with blueprint name

💡 Hint

Check where the route decorator is applied.

The route is decorated on app instead of v1 blueprint. So it is not part of the /api/v1 prefix routes. Accessing /api/v1/hello returns 404 because no such route exists under the blueprint.

🧠 Conceptual

expert

How does Flask blueprint versioning help in API maintenance?

Why is using blueprints with URL prefixes for API versioning a good practice in Flask applications?

A It merges all API versions into a single route for simplicity

B It automatically upgrades old API versions to the latest without code changes

C It allows separating code for different API versions cleanly and enables running multiple versions simultaneously

D It forces all clients to use the newest API version only

💡 Hint

Think about how versioning affects code organization and client support.

Blueprints with URL prefixes let you keep different API versions in separate code modules. This helps maintain old versions while developing new ones and allows clients to choose which version to use.