Blueprint creation and registration in Flask - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What is the output when accessing the registered blueprint route?

Given the Flask app with a blueprint registered under '/shop', what will be the response when visiting '/shop/items'?

Flask

from flask import Flask, Blueprint

shop_bp = Blueprint('shop', __name__)

@shop_bp.route('/items')
def items():
    return 'Shop Items List'

app = Flask(__name__)
app.register_blueprint(shop_bp, url_prefix='/shop')

# What is the output of a GET request to '/shop/items'?

A Shop Items List

B 404 Not Found

C Internal Server Error

D Method Not Allowed

💡 Hint

Think about how url_prefix affects blueprint routes.

The blueprint 'shop_bp' is registered with the prefix '/shop'. The route '/items' inside the blueprint becomes '/shop/items' in the app. So accessing '/shop/items' returns 'Shop Items List'.

📝 Syntax

intermediate

Which option correctly creates and registers a blueprint?

Select the code snippet that correctly creates a Flask blueprint named 'admin' and registers it with the app under '/admin'.

A

admin_bp = Blueprint('admin')
app = Flask(__name__)
app.register_blueprint(admin_bp, url_prefix='/admin')

B

admin_bp = Blueprint('admin', __name__)
app = Flask(__name__)
app.register_blueprint(admin_bp, url_prefix='/admin')

C

admin_bp = Blueprint('admin', __name__)
app = Flask(__name__)
app.register_blueprint(admin_bp, prefix='/admin')

D

admin_bp = Blueprint('admin', __name__)
app = Flask(__name__)
app.register_blueprint(admin_bp, url='/admin')

💡 Hint

Check the Blueprint constructor and register_blueprint parameters.

Blueprint requires two arguments: name and import name (__name__). The url prefix is set with url_prefix, not prefix or url.

🔧 Debug

advanced

Why does this blueprint route cause a 404 error?

Consider this code snippet: from flask import Flask, Blueprint api = Blueprint('api', __name__) @api.route('/data') def data(): return 'API Data' app = Flask(__name__) # Missing blueprint registration # What happens when you visit '/data' and why?

A 200 OK with response 'API Data' because blueprint routes are auto-registered

B 500 Internal Server Error due to missing route handler

C 404 Not Found because the blueprint was never registered with the app

D 405 Method Not Allowed because GET is not allowed

💡 Hint

Think about what happens if you define a blueprint but don't register it.

Blueprint routes only become active when the blueprint is registered with the Flask app. Without registration, the app does not know about '/data' route, so it returns 404.

❓ state_output

advanced

What is the output of this blueprint route using url variables?

Given the blueprint and route below, what is the output when visiting '/blog/post/42'?

Flask

from flask import Flask, Blueprint

blog_bp = Blueprint('blog', __name__)

@blog_bp.route('/post/<int:post_id>')
def show_post(post_id):
    return f'Post ID: {post_id}'

app = Flask(__name__)
app.register_blueprint(blog_bp, url_prefix='/blog')

A Post ID: post/42

B Post ID: <int:post_id>

C 404 Not Found

D Post ID: 42

💡 Hint

Look at how url variables are passed to the route function.

The route captures the integer 42 from the URL and passes it as post_id to the function, which returns 'Post ID: 42'.

🧠 Conceptual

expert

What happens if two blueprints have overlapping routes without url_prefix?

If you create two blueprints, both defining a route for '/' and register both without url_prefix, what will happen when you visit '/' in the Flask app?

A The route from the blueprint registered last will override the first, so only one response is served

B Both routes will be merged and served together in the response

C Flask will raise a runtime error due to route conflict

D Both routes will be served alternately on each request

💡 Hint

Think about how Flask handles route conflicts in registration order.

Flask registers routes in the order blueprints are registered. If two routes have the same URL, the last registered route overrides the previous one silently.