Why patterns improve code quality in Flask - See It in Action

Why patterns improve code quality

📖 Scenario: You are building a simple Flask web app to show a list of books. You want to organize your code well so it is easy to read and change later.

🎯 Goal: Build a Flask app that uses a pattern to separate data setup, configuration, core logic, and final app run. This will show how patterns help keep code clean and maintainable.

📋 What You'll Learn

Create a list of books as initial data

Add a configuration variable for minimum rating

Use a function to filter books by rating

Complete the Flask app with a route to display filtered books

💡 Why This Matters

🌍 Real World

Organizing Flask apps with clear patterns helps teams build and maintain web apps efficiently.

💼 Career

Understanding code patterns is essential for writing clean, scalable backend code in professional web development.

1

DATA SETUP: Create the initial data list

Create a list called books with these exact dictionaries: {'title': 'Book A', 'rating': 4.5}, {'title': 'Book B', 'rating': 3.8}, and {'title': 'Book C', 'rating': 4.9}.

Flask

# Your code here

Need a hint?

Think of books as a shelf holding your book info.

2

CONFIGURATION: Add a minimum rating variable

Create a variable called min_rating and set it to 4.0 to filter books by rating.

Flask

books = [
    {'title': 'Book A', 'rating': 4.5},
    {'title': 'Book B', 'rating': 3.8},
    {'title': 'Book C', 'rating': 4.9}
]
# Your code here

Need a hint?

This sets the bar for which books to show.

3

CORE LOGIC: Filter books by minimum rating

Create a function called get_top_books() that returns a list of books from books where the rating is greater than or equal to min_rating.

Flask

books = [
    {'title': 'Book A', 'rating': 4.5},
    {'title': 'Book B', 'rating': 3.8},
    {'title': 'Book C', 'rating': 4.9}
]
min_rating = 4.0
# Your code here

Need a hint?

Use a list comprehension inside the function to pick books with rating above the threshold.

4

COMPLETION: Build the Flask app route to show filtered books

Import Flask and render_template_string, create a Flask app called app, and add a route / that returns an HTML string listing the titles of books from get_top_books().

Flask

books = [
    {'title': 'Book A', 'rating': 4.5},
    {'title': 'Book B', 'rating': 3.8},
    {'title': 'Book C', 'rating': 4.9}
]
min_rating = 4.0

def get_top_books():
    return [book for book in books if book['rating'] >= min_rating]

# Your code here

Need a hint?

This final step shows how patterns help organize your Flask app clearly.