Flask project structure conventions - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What happens when you run this Flask app with this structure?

Consider a Flask app with this structure:

myapp/
  app.py
  templates/
    home.html
  static/
    style.css

The app.py contains:

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

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

What will the app do when you visit the root URL?

Flask

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

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

A Serve the style.css file automatically at the root URL.

B Raise a TemplateNotFound error because templates folder is missing.

C Render the home.html template from the templates folder successfully.

D Return a 404 error because no route is defined.

💡 Hint

Flask looks for templates in the templates folder by default.

Flask automatically finds templates in the templates folder inside the project directory. The route '/' renders home.html correctly.

📝 Syntax

intermediate

Which folder is Flask expecting for static files by default?

In a standard Flask project, where should you place CSS, JavaScript, and image files so Flask can serve them automatically?

A assets

B static

C public

D resources

💡 Hint

Flask uses a default folder name for static files.

Flask serves static files from the static folder by default.

🔧 Debug

advanced

Why does this Flask app fail to find the template?

Given this project structure:

myapp/
  app/
    __init__.py
    routes.py
  templates/
    index.html

And app/__init__.py contains:

from flask import Flask
app = Flask(__name__)

from app import routes

But running the app raises TemplateNotFound when rendering index.html. What is the likely cause?

Flask

from flask import Flask
app = Flask(__name__)

from app import routes

A The __init__.py file is missing a route decorator.

B The templates folder must be renamed to 'views' for Flask to find it.

C Flask cannot find templates because the app variable is not named 'application'.

D The Flask app is created in a subpackage, so the templates folder should be inside the app folder.

💡 Hint

Flask looks for templates relative to the app package location.

When the Flask app is created inside a package (app), Flask expects the templates folder inside that package folder. Having templates outside causes TemplateNotFound.

🧠 Conceptual

advanced

What is the purpose of the __init__.py file in a Flask app package?

In a Flask project structured as a package, why do we include an __init__.py file inside the app folder?

A It marks the folder as a Python package and initializes the Flask app instance.

B It contains all the HTML templates for the app.

C It stores static files like CSS and JavaScript.

D It is required to run the Flask development server.

💡 Hint

Think about Python packages and app initialization.

The __init__.py file makes the folder a Python package and usually contains the Flask app creation code.

❓ state_output

expert

How many routes are registered in this Flask app structure?

Given this Flask project structure:

myapp/
  app/
    __init__.py
    routes.py
  run.py

With app/__init__.py:

from flask import Flask
app = Flask(__name__)

from app import routes

And app/routes.py:

from app import app

@app.route('/')
def home():
    return 'Home'

@app.route('/about')
def about():
    return 'About'

And run.py:

from app import app

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

How many routes will the app have when running?

Flask

from flask import Flask
app = Flask(__name__)

from app import routes

# routes.py
from app import app

@app.route('/')
def home():
    return 'Home'

@app.route('/about')
def about():
    return 'About'

# run.py
from app import app

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

A 2 routes: '/' and '/about'

B 3 routes including a default error handler

C No routes registered because routes.py is not imported

D 1 route: '/' only

💡 Hint

Check where routes are defined and imported.

Both routes '/' and '/about' are defined in routes.py, which is imported in __init__.py, so both are registered.