Database query optimization in Flask - Mini Project: Build & Apply

Database Query Optimization with Flask

📖 Scenario: You are building a simple Flask web app that shows a list of books from a database. The database has many books, but you want to show only the books with more than 300 pages to users.

🎯 Goal: Build a Flask app that queries the database efficiently to get only books with more than 300 pages and displays their titles.

📋 What You'll Learn

Create a list of book dictionaries with title and pages

Add a variable to set the minimum page count filter

Use a list comprehension to select books with pages greater than the filter

Create a Flask route to display the filtered book titles

💡 Why This Matters

🌍 Real World

Filtering data before sending it to users helps apps run faster and use less memory.

💼 Career

Knowing how to optimize queries and filter data efficiently is important for backend web development jobs.

1

Create the book data list

Create a list called books with these exact dictionaries: {'title': 'Python Basics', 'pages': 250}, {'title': 'Flask Web Development', 'pages': 350}, {'title': 'Advanced Python', 'pages': 400}

Flask

# Create the list of books with title and pages
# Your code here

Need a hint?

Use a list with dictionaries. Each dictionary has keys 'title' and 'pages'.

2

Set the minimum page count filter

Create a variable called min_pages and set it to 300 to filter books with more than 300 pages

Flask

books = [
    {'title': 'Python Basics', 'pages': 250},
    {'title': 'Flask Web Development', 'pages': 350},
    {'title': 'Advanced Python', 'pages': 400}
]
# Set the minimum pages filter
# Your code here

Need a hint?

Just create a variable named min_pages and assign 300.

3

Filter books with list comprehension

Create a list called filtered_books using a list comprehension that includes only books from books where the pages value is greater than min_pages

Flask

books = [
    {'title': 'Python Basics', 'pages': 250},
    {'title': 'Flask Web Development', 'pages': 350},
    {'title': 'Advanced Python', 'pages': 400}
]
min_pages = 300
# Filter books with pages > min_pages
# Your code here

Need a hint?

Use a list comprehension with book for book in books if book['pages'] > min_pages.

4

Create Flask route to display filtered books

Import Flask and create an app. Then add a route /books that returns a string with the titles of filtered_books joined by commas

Flask

books = [
    {'title': 'Python Basics', 'pages': 250},
    {'title': 'Flask Web Development', 'pages': 350},
    {'title': 'Advanced Python', 'pages': 400}
]
min_pages = 300
filtered_books = [book for book in books if book['pages'] > min_pages]

# Import Flask and create app
# Add route /books to show titles
# Your code here

Need a hint?

Import Flask, create app, define route /books, and return joined titles.