Blueprint routes and templates in Flask - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What is the output when accessing a Blueprint route?

Given this Flask Blueprint setup, what will the browser display when visiting /blog/?

Flask

from flask import Blueprint, render_template_string

blog = Blueprint('blog', __name__, template_folder='templates')

@blog.route('/')
def index():
    return render_template_string('<h1>Blog Home</h1>')

# Assume app.register_blueprint(blog, url_prefix='/blog') is done

A 404 Not Found error

B <h1>Blog Home</h1>

C 500 Internal Server Error

D Empty page with status 200

💡 Hint

Think about how Blueprint routes are registered with a URL prefix.

The Blueprint 'blog' is registered with the prefix '/blog'. The route '/' inside the Blueprint corresponds to '/blog/' in the app. The function returns a simple HTML heading, so the browser shows '

Blog Home

'.

📝 Syntax

intermediate

Identify the syntax error in Blueprint route definition

Which option contains a syntax error in defining a Flask Blueprint route?

Flask

from flask import Blueprint

api = Blueprint('api', __name__)

@api.route('/data')
def get_data():
    return 'Data response'

A

@api.route('/data')
def get_data()
    return 'Data response'

B

@api.route('/data')
def get_data():
    return 'Data response'

C

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D

api.route('/data')
def get_data():
    return 'Data response'

💡 Hint

Check for missing colons and indentation.

Option A is missing a colon after the function definition, causing a SyntaxError. Options A, C, and D are identical and correct.

❓ state_output

advanced

What template is rendered by this Blueprint route?

Given this Blueprint and template setup, what will be rendered when visiting /shop/?

Flask

from flask import Blueprint, render_template

shop = Blueprint('shop', __name__, template_folder='shop_templates')

@shop.route('/')
def home():
    return render_template('home.html')

# Assume app.register_blueprint(shop, url_prefix='/shop')

# Content of shop_templates/home.html:
# <h2>Welcome to the Shop</h2>

A <h2>Welcome to the Shop</h2>

B <h1>Shop Home</h1>

C TemplateNotFound error

D Empty response with status 200

💡 Hint

Check the template folder specified in the Blueprint and the template file name.

The Blueprint specifies 'shop_templates' as its template folder. The route renders 'home.html' from that folder, which contains '

Welcome to the Shop

'. So this HTML is rendered.

🔧 Debug

advanced

Why does this Blueprint route cause a 404 error?

Consider this Blueprint code and registration. Why does visiting /admin/dashboard return 404?

Flask

from flask import Blueprint

admin = Blueprint('admin', __name__)

@admin.route('/dashboard')
def dashboard():
    return 'Admin Dashboard'

# In main app:
# app.register_blueprint(admin, url_prefix='/admin/')

A The function 'dashboard' is missing a return statement.

B The route '/dashboard' inside Blueprint is incorrect syntax.

C The url_prefix has a trailing slash causing route mismatch.

D Blueprint name 'admin' conflicts with Flask reserved keywords.

💡 Hint

Check how url_prefix with trailing slash affects route matching.

Using url_prefix='/admin/' adds a trailing slash to the prefix. Flask concatenates this with the route '/dashboard' resulting in '/admin//dashboard' which does not match '/admin/dashboard'. This causes a 404 error. Removing the trailing slash in url_prefix fixes the issue.

🧠 Conceptual

expert

How does Flask resolve templates in nested Blueprints?

If you have a Blueprint 'store' with template_folder='templates/store' and inside it a nested Blueprint 'products' with template_folder='templates/store/products', which template path will Flask look for when rendering render_template('list.html') inside 'products' Blueprint?

A templates/list.html

B templates/store/products/templates/list.html

C templates/store/list.html

D templates/store/products/list.html

💡 Hint

Blueprints use their own template_folder as base for render_template calls inside them.

Each Blueprint uses its own template_folder as the root for templates. The nested 'products' Blueprint has template_folder='templates/store/products', so render_template('list.html') looks inside that folder. It does not fallback to parent Blueprint folders automatically.