Introduction

Welcome to this blog series on building data-driven web applications using Flask and SQLAlchemy. Flask is a lightweight and flexible Python framework, while SQLAlchemy provides a powerful Object Relational Mapper (ORM) for interacting with databases.

This series will guide you through the process of creating web applications that store, retrieve, and manipulate data using these powerful tools.

In this first part, we will focus on setting up our development environment and establishing a basic understanding of Flask and SQLAlchemy.

Setting Up the Environment

1. Python and Virtual Environment

Ensure you have Python installed on your system. Create a virtual environment to manage dependencies:

    python -m venv myenv
    source myenv/bin/activate 
    

2. Installing Flask and SQLAlchemy

Install Flask and SQLAlchemy within your virtual environment:

    pip install Flask SQLAlchemy
    

Creating a Basic Flask Application

1. The Flask App

Let's create our first Flask application, "app.py":

    from flask import Flask

    app = Flask(__name__)

    @app.route('/')
    def index():
      return 'Welcome to our Flask app!'

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

2. Running the App

Navigate to the directory containing "app.py" and run the following:

    flask run
    

This will launch your Flask application, and you can access it at "http://127.0.0.1:5000/".

Integrating SQLAlchemy

1. Defining a Database Model

Let's create a model for storing user information in a database:

    from sqlalchemy import Column, Integer, String
    from sqlalchemy.ext.declarative import declarative_base

    Base = declarative_base()

    class User(Base):
      __tablename__ = 'users'
      id = Column(Integer, primary_key=True)
      name = Column(String(50), nullable=False)
      email = Column(String(100), unique=True, nullable=False)
    

2. Creating a Database Connection

We need to configure our Flask app to connect to the database. Let's add database settings to our "app.py":

    from sqlalchemy import create_engine
    from sqlalchemy.orm import sessionmaker

    # Database configuration
    DATABASE_URL = 'sqlite:///mydatabase.db'

    engine = create_engine(DATABASE_URL)
    SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)

    Base.metadata.create_all(bind=engine)
    

Conclusion

This concludes the first part of our blog series. We have successfully set up our development environment, created a basic Flask application, and integrated SQLAlchemy for database interactions. In subsequent parts, we will explore creating dynamic web pages, handling user input, and building more complex features.

Page 2: Creating Dynamic Web Pages with Flask and SQLAlchemy

Rendering Templates with Jinja

1. Installing Jinja

Jinja is a powerful templating engine for Flask. Install it using:

    pip install Jinja2
    

2. Creating a Template

Create a new file named "index.html" in a folder named "templates" in your project root. This will be our template for the home page: