In this lesson, you will learn about error handling and debugging in Python web development. Understanding how to manage errors and fix bugs is crucial for building reliable applications. You will create a simple Flask app that interacts with a database, intentionally introduce errors, and learn how to handle and debug them.

By the end, you will know how to use try-except blocks for error handling, debug code in VS Code, and avoid common pitfalls like incorrect database connections or unhandled exceptions.

First, you need to create a new folder for this lesson's project and set up the environment.

1. Open VS Code.
2. Create a new folder on your computer called 'FlaskErrorHandling'.
3. Open this folder in VS Code (File > Open Folder).

Next, create a virtual environment to manage your project's dependencies.

1. Open the Command Palette: View > Command Palette.
2. Type 'Python: Create Environment' and select it.
3. Choose 'Venv'.
4. Select your Python version.
5. VS Code will create a '.venv' folder.

Next, Open a terminal in VS Code to install Flask.

1. Go to View > Terminal.
2. Run: pip install flask.
3. Wait for the installation to complete. 

You will create a sample SQLite database with a 'users' table. This will be used in your Flask app.

Create a new file called 'create_db.py' in your project folder and add the following code:

import sqlite3

conn = sqlite3.connect('users.db')
c = conn.cursor()

c.execute('''CREATE TABLE IF NOT EXISTS users
             (id INTEGER PRIMARY KEY,
              name TEXT NOT NULL,
              age INTEGER NOT NULL)''')

# Insert sample data
c.execute("INSERT INTO users (name, age) VALUES ('Alice', 25)")
c.execute("INSERT INTO users (name, age) VALUES ('Bob', 30)")

conn.commit()
conn.close()
print('Database created successfully!')

Run this script in the terminal: python create_db.py.

Now, create a basic Flask app to display users from the database. This will be the foundation where we introduce errors.

Create a file called 'app.py' and add the following code:

from flask import Flask, render_template
import sqlite3

app = Flask(__name__)

@app.route('/')
def home():
    conn = sqlite3.connect('users.db')
    c = conn.cursor()
    c.execute("SELECT * FROM users")
    users = c.fetchall()
    conn.close()
    return render_template('users.html', users=users)

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

Create a 'templates' folder and then create the 'users.html' in it with:

<!DOCTYPE html>
<html>
<head><title>Users</title></head>
<body>
<h1>Users</h1>
<table border="1">
    <tr><th>ID</th><th>Name</th><th>Age</th></tr>
    {% for user in users %}
    <tr><td>{{ user[0] }}</td><td>{{ user[1] }}</td><td>{{ user[2] }}</td></tr>
    {% endfor %}
</table>
</body>
</html>