Introduction

Flask models and SQLAlchemy are essential tools for managing and working with data in Flask applications. In this guide, we'll explore how to create and use Flask models to interact with databases using SQLAlchemy, a popular Object-Relational Mapping (ORM) library.

Step 1: Setting Up Your Flask Application

Before working with models, make sure you have a Flask application. If not, you can create a basic Flask app like this:

from flask import Flask
from flask_sqlalchemy import SQLAlchemy
app = Flask(__name)
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///your_database.db'
db = SQLAlchemy(app)
        

Make sure to install Flask-SQLAlchemy if you haven't already by running pip install Flask-SQLAlchemy.

Step 2: Creating a Model

To define a model, you can create a Python class that represents a table in your database. Here's an example of a simple model:

class User(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    username = db.Column(db.String(80), unique=True, nullable=False)
    email = db.Column(db.String(120), unique=True, nullable=False)
    def __init__(self, username, email):
        self.username = username
        self.email = email
        

In this example, we define a "User" model with three fields: "id," "username," and "email." The model class inherits from db.Model, and the fields are defined as class attributes.

Step 3: Creating Database Tables

To create the database tables based on your models, you can run the following commands in your Python script:

# Create the database tables
db.create_all()
        

This command initializes the database schema based on your defined models.

Step 4: Interacting with the Database

With your models in place, you can interact with the database by using SQLAlchemy methods. Here's an example of how to add a new user to the database:

# Create a new user
new_user = User(username='john_doe', email='john@example.com')
# Add the user to the database
db.session.add(new_user)
db.session.commit()
        

This code creates a new user object, adds it to the session, and commits the changes to the database.

Conclusion

Flask models and SQLAlchemy provide a powerful way to manage data in your Flask applications. By defining models, creating database tables, and using SQLAlchemy to interact with the database, you can build data-driven web applications with ease.