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Login System with Python Flask and MySQL

Updated on by David Adams

Login System with Python Flask and MySQL

In this tutorial, we'll be creating a complete login and registration system with Python Flask and MySQL.

Python is currently taking the web development scene by storm, growing consistently every year. It has a low learning curve and therefore much easier to adapt to compared to other known languages (Node.js, PHP, etc.). In addition, Python is relatively new, so it would be advantageous to start learning immediately.

The Advanced package includes additional features and a download link to the source code.

1. Getting Started

There are a few steps we need to take before we create our python login and registration system. We need to download and set-up Python and install the packages that our app will depend on.

1.1. What You Will Learn in this Tutorial

  • Form Design — Design a login and registration form with HTML5 and CSS3.
  • Templates — Create Flask templates with HTML and Python.
  • Basic Validation — Validating form data that is sent to the server (username, password, and email).
  • Session Management — Initialize sessions and store retrieved database results.
  • MySQL Queries — Select and insert records from/in our database table.
  • Routes — Routing will enable us to associate the URLs with the functions that we will create.

1.2. Requirements

  • Download and install Python, for this tutorial I'll be using Python 3.7.2. Make sure to check the Add Python to PATH option on the installation setup screen.
  • Download and install MySQL Community Server and MySQL Workbench. You can skip this step if you already have a MySQL server installed.
  • Open command line and Install Python Flask with the command: pip install flask
  • Install Flask-MySQLdb with the command: pip install flask-mysqldb

1.3. File Structure & Setup

We need to create our project directory and files. You can create the directory anywhere on your computer, as long as Python can access it. Create the directories and files below.

File Structure

\-- pythonlogin
    |-- main.py
    \-- static
        |-- style.css
    \-- templates
        |-- index.html
        |-- register.html
        |-- home.html
        |-- profile.html
        |-- layout.html

Each file will contain the following:

  • main.py — This will be our main project file, all our Python code will be in this file (Routes, MySQL connection, validation, etc).
  • index.html — The login form template created with HTML5 and CSS3.
  • register.html — The registration form template created with HTML5 and CSS3.
  • home.html — The home template which is restricted to logged-in users.
  • profile.html — The profile template which is restricted to logged-in users. The user's details will be populated on this page.
  • layout.html — The layout template for the home and profile templates.
  • style.css — The CSS3 stylesheet for our login and registration system.

The below instruction will start your web server (Windows):

  • Make sure your MySQL server is up and running. It should have automatically started if you installed it via the installer. In addition, ensure MySQL is running on port 3306 otherwise you'll encounter connection errors.
  • Open Command Prompt and navigate to your project directory. You can do this with the command cd c:\your_project_folder_destination on Windows.
  • Run command: set FLASK_APP=main.py
  • Run command: set FLASK_DEBUG=1
  • Run command: flask run

Debug mode will enable us to edit our files without constantly restarting the web server.

2. Creating the Database and setting-up Tables

MySQL Workbench is a GUI for managing our databases. Follow the below instructions on how to get started.

  • Open MySQL Workbench
  • Enter your MySQL details
  • Click Test Connection. If successful, you can click OK
  • Open your connection
  • Execute the following SQL statement:
SQL Copy
CREATE DATABASE IF NOT EXISTS `pythonlogin` DEFAULT CHARACTER SET utf8 COLLATE utf8_general_ci;
USE `pythonlogin`;

CREATE TABLE IF NOT EXISTS `accounts` (
	`id` int(11) NOT NULL AUTO_INCREMENT,
  	`username` varchar(50) NOT NULL,
  	`password` varchar(255) NOT NULL,
  	`email` varchar(100) NOT NULL,
    PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=2 DEFAULT CHARSET=utf8;

INSERT INTO `accounts` (`id`, `username`, `password`, `email`) VALUES (1, 'test', 'test', 'test@test.com');

MySQL Workbench Execute Login System SQL

The above SQL statement will create our database pythonlogin with the table accounts, along with a test account that we can use for testing purposes.

3. Creating the Stylesheet (CSS3)

Edit the style.css file and add the following:

CSS Copy
* {
  	box-sizing: border-box;
  	font-family: -apple-system, BlinkMacSystemFont, "segoe ui", roboto, oxygen, ubuntu, cantarell, "fira sans", "droid sans", "helvetica neue", Arial, sans-serif;
  	font-size: 16px;
  	-webkit-font-smoothing: antialiased;
  	-moz-osx-font-smoothing: grayscale;
}
body {
  	background-color: #435165;
  	margin: 0;
}
.login, .register {
  	width: 400px;
  	background-color: #ffffff;
  	box-shadow: 0 0 9px 0 rgba(0, 0, 0, 0.3);
  	margin: 100px auto;
}
.login h1, .register h1 {
  	text-align: center;
  	color: #5b6574;
  	font-size: 24px;
  	padding: 20px 0 20px 0;
  	border-bottom: 1px solid #dee0e4;
}
.login .links, .register .links {
  	display: flex;
  	padding: 0 15px;
}
.login .links a, .register .links a {
  	color: #adb2ba;
  	text-decoration: none;
  	display: inline-flex;
  	padding: 0 10px 10px 10px;
  	font-weight: bold;
}
.login .links a:hover, .register .links a:hover {
  	color: #9da3ac;
}
.login .links a.active, .register .links a.active {
  	border-bottom: 3px solid #3274d6;
  	color: #3274d6;
}
.login form, .register form {
  	display: flex;
  	flex-wrap: wrap;
  	justify-content: center;
  	padding-top: 20px;
}
.login form label, .register form label {
  	display: flex;
  	justify-content: center;
  	align-items: center;
  	width: 50px;
  	height: 50px;
  	background-color: #3274d6;
  	color: #ffffff;
}
.login form input[type="password"], .login form input[type="text"], .login form input[type="email"], .register form input[type="password"], .register form input[type="text"], .register form input[type="email"] {
  	width: 310px;
  	height: 50px;
  	border: 1px solid #dee0e4;
  	margin-bottom: 20px;
  	padding: 0 15px;
}
.login form input[type="submit"], .register form input[type="submit"] {
  	width: 100%;
  	padding: 15px;
  	margin-top: 20px;
  	background-color: #3274d6;
  	border: 0;
  	cursor: pointer;
  	font-weight: bold;
  	color: #ffffff;
  	transition: background-color 0.2s;
}
.login form input[type="submit"]:hover, .register form input[type="submit"]:hover {
  	background-color: #2868c7;
  	transition: background-color 0.2s;
}
.navtop {
  	background-color: #2f3947;
  	height: 60px;
  	width: 100%;
  	border: 0;
}
.navtop div {
  	display: flex;
  	margin: 0 auto;
  	width: 1000px;
  	height: 100%;
}
.navtop div h1, .navtop div a {
  	display: inline-flex;
  	align-items: center;
}
.navtop div h1 {
  	flex: 1;
  	font-size: 24px;
  	padding: 0;
 	margin: 0;
  	color: #eaebed;
  	font-weight: normal;
}
.navtop div a {
  	padding: 0 20px;
  	text-decoration: none;
  	color: #c1c4c8;
  	font-weight: bold;
}
.navtop div a i {
  	padding: 2px 8px 0 0;
}
.navtop div a:hover {
  	color: #eaebed;
}
body.loggedin {
  	background-color: #f3f4f7;
}
.content {
  	width: 1000px;
  	margin: 0 auto;
}
.content h2 {
  	margin: 0;
  	padding: 25px 0;
  	font-size: 22px;
  	border-bottom: 1px solid #e0e0e3;
  	color: #4a536e;
}
.content > p, .content > div {
  	box-shadow: 0 0 5px 0 rgba(0, 0, 0, 0.1);
  	margin: 25px 0;
  	padding: 25px;
	background-color: #fff;
}
.content > p table td, .content > div table td {
	padding: 5px;
}
.content > p table td:first-child, .content > div table td:first-child {
	font-weight: bold;
	color: #4a536e;
	padding-right: 15px;
}
.content > div p {
	padding: 5px;
	margin: 0 0 10px 0;
}

The above stylesheet will structure our pages and provide an innovative experience for our users. Feel free to customize the stylesheet (change text color, font sizes, content width, etc).

4. Creating the Login System

We can finally start coding with Python! What we'll do in this section is create the login template, connect to our MySQL database, implement login authentication, and define session variables.

The first thing we need to do is import the packages we're going to use, edit the main.py file, and add the following:

Python Copy
from flask import Flask, render_template, request, redirect, url_for, session
from flask_mysqldb import MySQL
import MySQLdb.cursors
import re

Now that we have imported all the packages we're going to use, we need to create the MySQL and app related variables and configure the MySQL connection details.

Add after:

Python Copy
app = Flask(__name__)

# Change this to your secret key (can be anything, it's for extra protection)
app.secret_key = 'your secret key'

# Enter your database connection details below
app.config['MYSQL_HOST'] = 'localhost'
app.config['MYSQL_USER'] = 'root'
app.config['MYSQL_PASSWORD'] = ''
app.config['MYSQL_DB'] = 'pythonlogin'

# Intialize MySQL
mysql = MySQL(app)

Ensure to configure the MySQL variables to reflect your MySQL details.

Now we can proceed to create the login page. To do that, we need to create a new route. Routes will enable us to associate our functions with a particular URL.

Add after:

Python Copy
# http://localhost:5000/pythonlogin/ - the following will be our login page, which will use both GET and POST requests
@app.route('/pythonlogin/', methods=['GET', 'POST'])
def login():
    # Output message if something goes wrong...
    msg = ''
    return render_template('index.html', msg='')

4.1 Creating the Login Template

Edit the index.html file and add:

HTML Copy
<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title>Login</title>
		<link rel="stylesheet" href="{{ url_for('static', filename='style.css') }}">
		<link rel="stylesheet" href="https://use.fontawesome.com/releases/v5.7.1/css/all.css">
	</head>
	<body>
		<div class="login">
			<h1>Login</h1>
			<div class="links">
				<a href="{{ url_for('login') }}" class="active">Login</a>
				<a href="#">Register</a>
			</div>
			<form action="{{ url_for('login') }}" method="post">
				<label for="username">
					<i class="fas fa-user"></i>
				</label>
				<input type="text" name="username" placeholder="Username" id="username" required>
				<label for="password">
					<i class="fas fa-lock"></i>
				</label>
				<input type="password" name="password" placeholder="Password" id="password" required>
				<div class="msg">{{ msg }}</div>
				<input type="submit" value="Login">
			</form>
		</div>
	</body>
</html>

As you can see with the login template, we create the form along with the input fields: username and password. The form's method is set to post which determines the type of request we want to send to our server. We'll be using a POST request to send the form data.

If we navigate to http://localhost:5000/pythonlogin/ in our web browser, it will look like the following:

http://localhost:5000/pythonlogin/
Python MySQL Login Form

If you click the Login button, nothing will happen or will return an error, that's because we haven't implemented the code that handles the POST request.

4.2 Authenticating Users with Python

Now we need to go back to our main.py file and add the authentication code to our route function that we created.

After:

def login():
    # Output message if something goes wrong...
    msg = ''

Add:

Python Copy
    # Check if "username" and "password" POST requests exist (user submitted form)
    if request.method == 'POST' and 'username' in request.form and 'password' in request.form:
        # Create variables for easy access
        username = request.form['username']
        password = request.form['password']

With the code above, we use an if statement to check if the requested method is POST and check if the username and password variables exist in the form request. If they both exist, the username and password variables will be created, which will be associated with the form variables.

Add after:

Python Copy
        # Check if account exists using MySQL
        cursor = mysql.connection.cursor(MySQLdb.cursors.DictCursor)
        cursor.execute('SELECT * FROM accounts WHERE username = %s AND password = %s', (username, password,))
        # Fetch one record and return result
        account = cursor.fetchone()

The code above will execute a SQL query that will retrieve the account details from our accounts table in our MySQL database. The username and password variables are associated with this query as that is what we will use to find the account.

Add after:

Python Copy
        # If account exists in accounts table in out database
        if account:
            # Create session data, we can access this data in other routes
            session['loggedin'] = True
            session['id'] = account['id']
            session['username'] = account['username']
            # Redirect to home page
            return 'Logged in successfully!'
        else:
            # Account doesnt exist or username/password incorrect
            msg = 'Incorrect username/password!'

The code above will determine if the account exists. If it does, the session variables are declared. These session variables will be remembered for the user as they will be used to determine whether the user is logged-in or not.

Session variables basically act like browser cookies. They are stored on the server as opposed to the user's browser.

If the account doesn't exist, we can simply output the error on the login form.

Your login route should look like the following:

Python Copy
@app.route('/pythonlogin/', methods=['GET', 'POST'])
def login():
    # Output message if something goes wrong...
    msg = ''
    # Check if "username" and "password" POST requests exist (user submitted form)
    if request.method == 'POST' and 'username' in request.form and 'password' in request.form:
        # Create variables for easy access
        username = request.form['username']
        password = request.form['password']
        # Check if account exists using MySQL
        cursor = mysql.connection.cursor(MySQLdb.cursors.DictCursor)
        cursor.execute('SELECT * FROM accounts WHERE username = %s AND password = %s', (username, password,))
        # Fetch one record and return result
        account = cursor.fetchone()
        # If account exists in accounts table in out database
        if account:
            # Create session data, we can access this data in other routes
            session['loggedin'] = True
            session['id'] = account['id']
            session['username'] = account['username']
            # Redirect to home page
            return 'Logged in successfully!'
        else:
            # Account doesnt exist or username/password incorrect
            msg = 'Incorrect username/password!'
    # Show the login form with message (if any)
    return render_template('index.html', msg=msg)

To make sure everything is working correctly, navigate to http://localhost:5000/pythonlogin/ and input "test" in both the username and password fields, and then click the Login button. You should receive a message that outputs "Logged in successfully!".

4.3 Creating the Logout Script

For a user to logout, all we have to do is remove the session variables that were created when the user logged-in.

Add the following code to the main.py file:

Python Copy
# http://localhost:5000/python/logout - this will be the logout page
@app.route('/pythonlogin/logout')
def logout():
    # Remove session data, this will log the user out
   session.pop('loggedin', None)
   session.pop('id', None)
   session.pop('username', None)
   # Redirect to login page
   return redirect(url_for('login'))

The above code will remove each session variable associated with the user. Without these session variables, the user cannot be logged-in. Subsequently, the user is redirected to the login page.

We can logout by navigating to the following URL: http://localhost:5000/pythonlogin/logout

5. Creating the Registration System

We need a registration system that users can use to register on our app. What we'll do in this section is to create a new register route and create the registration template, along with the registration form, which will consist of input fields, submit button, etc.

5.1 Creating the Registration Template

Edit the register.html file and add:

HTML Copy
<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title>Register</title>
		<link rel="stylesheet" href="{{ url_for('static', filename='style.css') }}">
		<link rel="stylesheet" href="https://use.fontawesome.com/releases/v5.7.1/css/all.css">
	</head>
	<body>
		<div class="register">
			<h1>Register</h1>
			<div class="links">
				<a href="{{ url_for('login') }}">Login</a>
				<a href="{{ url_for('register') }}" class="active">Register</a>
			</div>
			<form action="{{ url_for('register') }}" method="post" autocomplete="off">
				<label for="username">
					<i class="fas fa-user"></i>
				</label>
				<input type="text" name="username" placeholder="Username" id="username" required>
				<label for="password">
					<i class="fas fa-lock"></i>
				</label>
				<input type="password" name="password" placeholder="Password" id="password" required>
				<label for="email">
					<i class="fas fa-envelope"></i>
				</label>
				<input type="email" name="email" placeholder="Email" id="email" required>
				<div class="msg">{{ msg }}</div>
				<input type="submit" value="Register">
			</form>
		</div>
	</body>
</html>

The HTML template above we'll use to register users. It's identical to the login template but also includes the Email input field.

The form's action attribute is associated with the "register" route, as we'll use this route to handle the POST request.

5.2 Registering Users with Python

Now that we have our template created, we can proceed to create the "register" route, which will handle the POST request and insert a new account into our accounts table, but only if the submitted fields are valid.

Go back to the main.py file and add the following:

Python Copy
# http://localhost:5000/pythinlogin/register - this will be the registration page, we need to use both GET and POST requests
@app.route('/pythonlogin/register', methods=['GET', 'POST'])
def register():
    # Output message if something goes wrong...
    msg = ''
    # Check if "username", "password" and "email" POST requests exist (user submitted form)
    if request.method == 'POST' and 'username' in request.form and 'password' in request.form and 'email' in request.form:
        # Create variables for easy access
        username = request.form['username']
        password = request.form['password']
        email = request.form['email']
    elif request.method == 'POST':
        # Form is empty... (no POST data)
        msg = 'Please fill out the form!'
    # Show registration form with message (if any)
    return render_template('register.html', msg=msg)

We create the "register" route and implement validation that will check if all the form fields exist. If they don't, then output a simple error.

After:

email = request.form['email']

Add:

Python Copy
        # Check if account exists using MySQL
        cursor = mysql.connection.cursor(MySQLdb.cursors.DictCursor)
        cursor.execute('SELECT * FROM accounts WHERE username = %s', (username,))
        account = cursor.fetchone()
        # If account exists show error and validation checks
        if account:
            msg = 'Account already exists!'
        elif not re.match(r'[^@]+@[^@]+\.[^@]+', email):
            msg = 'Invalid email address!'
        elif not re.match(r'[A-Za-z0-9]+', username):
            msg = 'Username must contain only characters and numbers!'
        elif not username or not password or not email:
            msg = 'Please fill out the form!'
        else:
            # Account doesnt exists and the form data is valid, now insert new account into accounts table
            cursor.execute('INSERT INTO accounts VALUES (NULL, %s, %s, %s)', (username, password, email,))
            mysql.connection.commit()
            msg = 'You have successfully registered!'

The above code will select an account with the submitted username and password fields. If the account doesn't exist, we can proceed to validate the input data. Validation will check if the submitted email is valid and check if the username contains only letters and numbers.

Subsequently, the code will insert a new account into our accounts tables.

To test that it is working correctly, navigate to http://localhost:5000/pythonlogin/register and fill out the form and click the Register button. You should receive the following response:

http://localhost:5000/pythonlogin/register
Python Registration Form

Now we can go back to our index.html file and change this line:

<a href="#">Register</a>

To:

HTML Copy
<a href="{{ url_for('register') }}">Register</a>

Users can now register and log in to our app. Next, we'll create a basic home page for logged-in users.

6. Creating the Home Page

The home page will be restricted to logged-in users only. Non-registered users cannot access this page. You can adapt this page and create more pages.

Edit the main.py file and add the following:

Python Copy
# http://localhost:5000/pythinlogin/home - this will be the home page, only accessible for loggedin users
@app.route('/pythonlogin/home')
def home():
    # Check if user is loggedin
    if 'loggedin' in session:
        # User is loggedin show them the home page
        return render_template('home.html', username=session['username'])
    # User is not loggedin redirect to login page
    return redirect(url_for('login'))

The above code will create the home route function. If the user is logged-in, they will have access to the home page. If not, they will be redirected to the login page.

Edit the home.html file and add the following:

HTML Copy
{% extends 'layout.html' %}

{% block title %}Home{% endblock %}

{% block content %}
<h2>Home Page</h2>
<p>Welcome back, {{ username }}!</p>
{% endblock %}

We also need to create the layout for our logged-in pages. Edit the layout.html file and add:

HTML Copy
<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title>{% block title %}{% endblock %}</title>
		<link rel="stylesheet" href="{{ url_for('static', filename='style.css') }}">
		<link rel="stylesheet" href="https://use.fontawesome.com/releases/v5.7.1/css/all.css">
	</head>
	<body class="loggedin">
		<nav class="navtop">
			<div>
				<h1>Website Title</h1>
                <a href="{{ url_for('home') }}"><i class="fas fa-home"></i>Home</a>
				<a href="{{ url_for('profile') }}"><i class="fas fa-user-circle"></i>Profile</a>
				<a href="{{ url_for('logout') }}"><i class="fas fa-sign-out-alt"></i>Logout</a>
			</div>
		</nav>
		<div class="content">
			{% block content %}{% endblock %}
		</div>
	</body>
</html>

Now we can easily extend the same layout for both the home and profile pages.

Currently, when a user logs in, there will be a basic output message, we can now change that to redirect the user to our new home page instead. Find the following code in the login route function:

return 'Logged in successfully!'

Replace with:

Python Copy
return redirect(url_for('home'))

The user will now be redirected to the home page when they log in. If we enter the test details into the login form and click the Login button, we will see the following:

http://localhost:5000/pythonlogin/home
Python Login Home Page

It's just a simple home page that will output the username. You can implement your own code later.

Next, we'll create the profile page and populate the user's details.

7. Creating the Profile Page

The profile page will populate all details associated with the account (username, password, and email).

Add the following route to the main.py file:

Python Copy
# http://localhost:5000/pythinlogin/profile - this will be the profile page, only accessible for loggedin users
@app.route('/pythonlogin/profile')
def profile():
    # Check if user is loggedin
    if 'loggedin' in session:
        # We need all the account info for the user so we can display it on the profile page
        cursor = mysql.connection.cursor(MySQLdb.cursors.DictCursor)
        cursor.execute('SELECT * FROM accounts WHERE id = %s', (session['id'],))
        account = cursor.fetchone()
        # Show the profile page with account info
        return render_template('profile.html', account=account)
    # User is not loggedin redirect to login page
    return redirect(url_for('login'))

The above code will create the profile route and retrieve all the account details from the database, but only if the user is logged-in.

Edit the profile.html file and add:

HTML Copy
{% extends 'layout.html' %}

{% block title %}Profile{% endblock %}

{% block content %}
<h2>Profile Page</h2>
<div>
    <p>Your account details are below:</p>
    <table>
        <tr>
            <td>Username:</td>
            <td>{{ account['username'] }}</td>
        </tr>
        <tr>
            <td>Password:</td>
            <td>{{ account['password'] }}</td>
        </tr>
        <tr>
            <td>Email:</td>
            <td>{{ account['email'] }}</td>
        </tr>
    </table>
</div>
{% endblock %}

The above code will extend the layout (layout.html) file that we created previously. If you navigate to the profile page, it will look like the following:

http://localhost:5000/pythonlogin/profile
Python Login Profile Page

That's basically it for the home and profile pages. The Advanced package includes the edit profile feature that will enable the user to change their username, password, and email.

Conclusion

Congratulations! You've successfully created your own login and registration system with Python Flask and MySQL. You're free to use the source code from this tutorial in your application(s).

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