Model definition in Flask - Mini Project: Build & Apply

Flask Model Definition

📖 Scenario: You are building a simple web app to store information about books in a library.Each book has a title, an author, and a year it was published.

🎯 Goal: Create a Flask model to represent a Book with the fields title, author, and year_published.

📋 What You'll Learn

Use Flask-SQLAlchemy to define the model

Create a model class named Book

Include fields: id (primary key), title (string), author (string), and year_published (integer)

💡 Why This Matters

🌍 Real World

Defining models is essential for building web apps that store and manage data like books, users, or products.

💼 Career

Understanding model definition with Flask and SQLAlchemy is a key skill for backend web developers working with Python.

1

Set up the Flask app and SQLAlchemy

Create a Flask app instance called app and initialize SQLAlchemy with db = SQLAlchemy(app).

Flask

# Create the Flask app and initialize SQLAlchemy
# Your code here

Need a hint?

Import Flask and SQLAlchemy. Then create app = Flask(__name__) and db = SQLAlchemy(app).

2

Create the Book model class

Define a class called Book that inherits from db.Model.

Flask

from flask import Flask
from flask_sqlalchemy import SQLAlchemy

app = Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///library.db'
db = SQLAlchemy(app)

# Define the Book model class
# Your code here

Need a hint?

Define class Book(db.Model): and add columns for id, title, author, and year_published.

3

Add a string representation method

Add a __repr__ method to the Book class that returns a string like <Book 'Title' by Author>.

Flask

from flask import Flask
from flask_sqlalchemy import SQLAlchemy

app = Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///library.db'
db = SQLAlchemy(app)

class Book(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    title = db.Column(db.String(100))
    author = db.Column(db.String(100))
    year_published = db.Column(db.Integer)

    # Add __repr__ method here
    # Your code here

Need a hint?

Define def __repr__(self): and return a formatted string with the book's title and author.

4

Create the database tables

Call db.create_all() to create the tables in the database.

Flask

from flask import Flask
from flask_sqlalchemy import SQLAlchemy

app = Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///library.db'
db = SQLAlchemy(app)

class Book(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    title = db.Column(db.String(100))
    author = db.Column(db.String(100))
    year_published = db.Column(db.Integer)

    def __repr__(self):
        return f""

# Create the database tables
# Your code here

Need a hint?

Use with app.app_context(): then call db.create_all() to create tables.