Static file optimization in Flask - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

How does Flask serve static files by default?

Consider a Flask app with a folder named static containing CSS and JS files. What happens when a browser requests /static/style.css?

A Flask cannot serve static files; a separate web server is needed.

B Flask automatically serves the file from the <code>static</code> folder without extra code.

C Flask serves static files only if <code>send_file()</code> is called in a route.

D Flask requires a route to be defined to serve static files manually.

💡 Hint

Think about Flask's default behavior for the static folder.

Flask automatically serves files placed in the static folder at the URL path /static/filename. No extra route is needed.

📝 Syntax

intermediate

Which Flask code snippet correctly sets cache timeout for static files?

You want to set a cache timeout of 1 hour (3600 seconds) for static files in Flask. Which code snippet achieves this?

A app = Flask(__name__, static_folder='static', static_url_path='/static', static_cache_timeout=3600)

B

app = Flask(__name__)
app.config['STATIC_CACHE_TIMEOUT'] = 3600

C

app = Flask(__name__)
app.static_cache_timeout = 3600

D

app = Flask(__name__)
app.config['SEND_FILE_MAX_AGE_DEFAULT'] = 3600

💡 Hint

Look for the Flask config key that controls static file cache timeout.

The correct config key is SEND_FILE_MAX_AGE_DEFAULT, which sets the cache timeout in seconds for static files.

❓ state_output

advanced

What is the output of this Flask static file URL generation?

Given this Flask code snippet, what is the output of url_for('static', filename='js/app.js')?

Flask

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

with app.test_request_context():
    print(url_for('static', filename='js/app.js'))

A /static/js/app.js

B /js/app.js

C /static/app.js

D /app.js

💡 Hint

Remember the default static URL path in Flask.

The url_for('static', filename='js/app.js') generates the URL path starting with /static/ followed by the filename.

🔧 Debug

advanced

Why does this Flask app not serve updated static files immediately?

A developer updates a CSS file in the static folder but the browser still shows the old style. What is the most likely cause?

A The static folder is misnamed; Flask cannot find the updated file.

B Flask does not reload static files automatically; the server must restart.

C Browser cache is serving the old file; cache headers need adjustment or cache busting.

D The CSS file is not linked correctly in the HTML template.

💡 Hint

Think about how browsers handle static files and caching.

Browsers cache static files aggressively. Without cache busting or proper cache headers, updated files may not load immediately.

🧠 Conceptual

expert

What is the best practice to optimize static file delivery in Flask for production?

Which approach is recommended to optimize static file delivery in a Flask production environment?

A Use a dedicated web server like Nginx or a CDN to serve static files, offloading Flask.

B Disable caching entirely to ensure users always get the latest static files.

C Embed static files inside Flask routes and serve them dynamically on each request.

D Serve static files directly from Flask using its built-in server with cache headers set.

💡 Hint

Consider performance and scalability for production environments.

Flask's built-in server is not optimized for static file delivery in production. Using a web server or CDN improves speed and reduces load on Flask.