Flask is a popular Python web framework that is known for its simplicity, flexibility, and easy-to-understand APIs. Flask-login is a popular extension that provides a user authentication system for Flask web applications. In this article, we will discuss how to add authentication and authorization with Flask-login.
The User Model
The User Model is the core of the authentication system. It defines the properties of a user, such as username, password, and email.
Flask-login requires the User Model to have several methods:
is_authenticated( ): returns True if the user is authenticated and False if not. is_active( ): returns True if the user is active and False if not.
is_anonymous( ): returns False for a regular user object, and True for an AnonymousUser object. get_id( ): returns a unique identifier for the user, as a string.
Here is an example of how to define a User Model in Flask:
from flask_login import UserMixin
from werkzeug.security import generate_password_hash, check_password_hash
class User(UserMixin, db.Model):
id = db.Column(db.Integer, primary_key=True)
username = db.Column(db.String(80), unique=True)
password_hash = db.Column(db.String(128))
email = db.Column(db.String(120), unique=True)
def __init__(self, username, password, email):
self.username = username
self.set_password(password)
self.email = email
def set_password(self, password):
self.password_hash = generate_password_hash(password)
def check_password(self, password):
return check_password_hash(self.password_hash, password)
The user_loader
The user_loader is a function that Flask-login calls to load a user from the User Model. The function takes an ID argument, which is the string that get_id( ) returns.
The function must return a User object if the ID is valid and None if it is not. Here is an example of how to define a user_loader function:
@login_manager.user_loader
def load_user(user_id):
return User.query.get(int(user_id))
The /reports Endpoint
The /reports endpoint is an example of how to secure a Flask route so that only authenticated users can see it.
Here is an example of how to secure a route using Flask-login:
@app.route(‘/reports’)
@login_required
def reports():
return ‘You are authorized to view this page.’
In this example, if a non-authenticated user tries to access the /reports endpoint, Flask-login will redirect them to the login page. After the user logs in, they will be redirected back to /reports.
Login and Logout
To handle user login and logout, you can create two routes: one to handle login and one to handle logout. Here is an example of how to implement login and logout routes in Flask:
@app.route(‘/login’, methods=[‘GET’, ‘POST’])
def login():
if current_user.is_authenticated:
return redirect(url_for(‘index’))
form = LoginForm()
if form.validate_on_submit():
user = User.query.filter_by(username=form.username.data).first()
if user is None or not user.check_password(form.password.data):
flash(‘Invalid username or password’)
return redirect(url_for(‘login’))
login_user(user, remember=form.remember_me.data)
return redirect(url_for(‘index’))
return render_template(‘login.html’, title=’Sign In’, form=form)
@app.route(‘/logout’)
def logout():
logout_user()
return redirect(url_for(‘index’))
Creating an Admin User
To create an admin user, you can add a new field to the User Model and then check if the user has the admin permission in the view function. Here is an example of how to create an admin user:
class User(UserMixin, db.Model):
id = db.Column(db.Integer, primary_key=True)
username = db.Column(db.String(80), unique=True)
password_hash = db.Column(db.String(128))
email = db.Column(db.String(120), unique=True)
admin = db.Column(db.Boolean, default=False)
In the view function, you can check if the current user has the admin permission using the current_user.is_admin property:
@app.route(‘/admin’)
@login_required
def admin():
if not current_user.is_admin:
abort(403)
return ‘You are authorized to view this page.’
The Flask Ecosystem
The Flask ecosystem encompasses the various extensions and plugins that can be used to enhance Flask applications. One such plugin is Flask-forum.
Flask-forum is a free and open-source forum application that is built using Flask and several Flask extensions.
Flask extensions for composition
Flask extensions provide pre-built functionality that can be easily added to Flask applications. Some of the most popular Flask extensions include Flask-Admin for managing application data, Flask-Assets for managing application assets, Flask-DebugToolbar for debugging, Flask-Markdown for rendering Markdown content, Flask-Script for running command-line scripts, Flask-Security for handling user authentication and authorization, Flask-SQLAlchemy for database management, and Flask-WTF for handling web forms.
Example of flask-forum
Flask-forum is a forum application that provides a platform for users to create and manage forums. It uses several Flask extensions to provide functionality such as user authentication and authorization, forum management, and content rendering.
Flask-forum is an example of how Flask extensions can be used to create complex applications quickly and easily.
List of Flask extensions used in flask-forum
Flask-Admin: For managing the application data. Flask-Assets: For managing application assets.
Flask-DebugToolbar: For debugging. Flask-Markdown: For rendering Markdown content.
Flask-Script: For running command-line scripts. Flask-Security: For handling user authentication and authorization.
Flask-SQLAlchemy: For database management. Flask-WTF: For handling web forms.
In conclusion, adding authentication and authorization with Flask-login is essential for securing Flask web applications. The user Model, user_loader, and endpoint security are fundamental components of Flask-login.
The Flask ecosystem provides many extensions that can be used to enhance Flask applications quickly and easily. Flask-forum is an excellent example of how Flask extensions can be used to create complex applications.
Flask is a popular Python web framework that is known for its simplicity, flexibility, and easy-to-understand APIs. Its popularity has grown significantly in recent years due to its lightweight nature compared to other Python web frameworks, such as Django. Flask is a micro-framework that allows developers to add only the necessary components to their applications, making it more scalable and efficient.
One of the key features that separates Flask from other frameworks is its simplicity and lack of “magic.”
Flask simplicity and lack of “magic”
Flask prides itself on being a simple and lightweight framework that allows developers to choose which components they want to use in their application. Unlike other web frameworks such as Django, Flask does not come bundled with a lot of pre-built functionality and relies on the user to implement the required features.
This allows the developer to have complete control over the application’s architecture and enables them to pick and choose the libraries and extensions they want to use. It also provides a more natural learning curve for new developers who are not familiar with Flask.
One of the essential features of Flask’s simplicity is that it does not rely on any “magic.” Magic refers to the convention-over-configuration approach that other frameworks use, which can sometimes be frustrating for developers, especially when they need to make customizations to their application. Flask takes a more straightforward approach to web development by not implementing too many built-in assumptions about how things should work.
Instead, it provides a set of lightweight tools to help the developer put together their application, their way. Another area where Flask differs from other web frameworks such as Django is in the routing mechanism.
In Flask, the developer defines the routes explicitly, which gives them a lot more control over the URL structure of their application. In contrast, Django’s URL routing is more automatic, which can make it more challenging to modify the URL structure, especially in larger applications.
The simplicity of Flask also makes it more appealing for creating small to medium-sized applications, where the development team does not need a lot of built-in features or advanced functionality. Flask’s lightweight nature means that it can deliver fast and efficient web applications without sacrificing too much in terms of functionality.
This has made it a popular choice for developers looking to build prototypes or create Minimum Viable Products. In conclusion, Flask’s simplicity and lack of “magic” make it an appealing choice for developers who want full control over their web application’s architecture and components.
Its lightweight nature enables developers to build scalable and efficient web applications that do not compromise on functionality. Flask’s explicit routing mechanism and minimalistic approach enable it to be more performance-focused than other web frameworks such as Django.
The popularity of Flask continues to grow, and its simple approach to web development is perfect for those looking to learn Python web development quickly and efficiently. In summary, Flask’s simplicity and lack of “magic” make it a popular choice for developers who want full control over their web application’s components and architecture.
Flask’s lightweight nature makes it efficient and performance-focused, providing scalable and efficient web applications without compromising on functionality. Flask’s explicit routing mechanism and minimalistic approach set it apart from other web frameworks such as Django by allowing developers to implement only the necessary components to their applications.
The primary takeaway from this article is that Flask is a micro-framework that enables developers to choose which libraries and extensions to use, providing complete control over the application’s development.