Python Flask Tutorial: Creating Dynamic Database-Driven Web Apps for Web Development

In this tutorial, we will explore how to create dynamic database-driven web applications using Flask, a popular web framework for Python. Flask is lightweight and flexible, making it an ideal choice for building small to medium-sized web applications.

Before we get started, make sure you have Python and Flask installed on your computer. You can install Flask using pip, the Python package manager, by running the following command in your terminal:

pip install Flask

You will also need a database management system such as SQLite, MySQL, or PostgreSQL to store and retrieve data for your web application. For the purposes of this tutorial, we will use SQLite, a lightweight database that is easy to set up and ideal for development and testing.

Step 1: Setting up the Flask application

Start by creating a new directory for your project and navigating to it in your terminal. Inside this directory, create a new Python file called app.py and open it in your preferred code editor.

In app.py, import Flask and create a new instance of the Flask application:

from flask import Flask

app = Flask(__name__)

Next, create a route for the home page of your web application:

@app.route('/')
def home():
    return 'Hello, World!'

Finally, run the Flask application by adding the following code at the bottom of app.py:

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

You can now run your Flask application by executing the app.py file in your terminal:

python app.py

Open a web browser and navigate to http://127.0.0.1:5000 to see the message "Hello, World!" displayed on the home page of your web application.

Step 2: Setting up the database

Before we can create dynamic database-driven web applications, we need to set up a database to store and retrieve data. For this tutorial, we will use SQLite, a lightweight database engine that does not require a separate server to run.

Create a new directory called data inside your project directory to store the SQLite database file. In app.py, import SQLite and create a new database connection:

import sqlite3

conn = sqlite3.connect('data/database.db')

Next, create a new SQLite database table to store some sample data. Add the following code to create a users table with id, name, and email columns:

with conn:
    cursor = conn.cursor()
    cursor.execute('''
        CREATE TABLE IF NOT EXISTS users (
            id INTEGER PRIMARY KEY AUTOINCREMENT,
            name TEXT,
            email TEXT
        )
    ''')

Step 3: Adding dynamic routes

Now that we have set up the Flask application and database, let’s create some dynamic routes to interact with the database. Add the following code to app.py to create a route that retrieves all users from the database and displays them on a web page:

@app.route('/users')
def users():
    with conn:
        cursor = conn.cursor()
        cursor.execute('SELECT * FROM users')
        users = cursor.fetchall()

    return f'Users: {users}'

You can now navigate to http://127.0.0.1:5000/users in your web browser to see a list of all users stored in the database.

Step 4: Adding a form to insert data

To allow users to insert new data into the database, we can create a form that submits data to the server. Add the following code to app.py to create a route that displays a form for users to enter their name and email:

from flask import request

@app.route('/add_user', methods=['GET', 'POST'])
def add_user():
    if request.method == 'POST':
        name = request.form['name']
        email = request.form['email']

        with conn:
            cursor = conn.cursor()
            cursor.execute('INSERT INTO users (name, email) VALUES (?, ?)', (name, email))

        return 'User added successfully!'

    return '''
        <form method="post">
            <label for="name">Name:</label>
            <input type="text" id="name" name="name"><br>
            <label for="email">Email:</label>
            <input type="email" id="email" name="email"><br>
            <input type="submit" value="Submit">
        </form>
    '''

Now, navigate to http://127.0.0.1:5000/add_user in your web browser to see a form that allows you to add new users to the database.

Step 5: Updating and deleting data

To allow users to update or delete data in the database, we can create additional routes that handle these actions. Add the following code to app.py to create routes for updating and deleting users:

@app.route('/update_user/<int:user_id>', methods=['GET', 'POST'])
def update_user(user_id):
    if request.method == 'POST':
        name = request.form['name']
        email = request.form['email']

        with conn:
            cursor = conn.cursor()
            cursor.execute('UPDATE users SET name = ?, email = ? WHERE id = ?', (name, email, user_id))

        return 'User updated successfully!'

    with conn:
        cursor = conn.cursor()
        cursor.execute('SELECT * FROM users WHERE id = ?', (user_id,))
        user = cursor.fetchone()

    return f'''
        <form method="post">
            <label for="name">Name:</label>
            <input type="text" id="name" name="name" value="{user[1]}"><br>
            <label for="email">Email:</label>
            <input type="email" id="email" name="email" value="{user[2]}"><br>
            <input type="submit" value="Submit">
        </form>
    '''

@app.route('/delete_user/<int:user_id>', methods=['GET', 'POST'])
def delete_user(user_id):
    with conn:
        cursor = conn.cursor()
        cursor.execute('DELETE FROM users WHERE id = ?', (user_id,))

    return 'User deleted successfully!'

You can now navigate to http://127.0.0.1:5000/update_user/<user_id> to update a specific user or http://127.0.0.1:5000/delete_user/<user_id> to delete a specific user from the database.

Congratulations! You have successfully created a dynamic database-driven web application using Flask and Python. Feel free to customize and expand upon this tutorial to create more complex web applications with additional features and functionality. Happy coding!