How to Setup User Login in Flask?

In this tutorial, we are going to use flask login library for our app user authentication.

So let's get started, How to use this.

• First, create a project folder and in this folder make a virtual environment for our project.
• Here I am using pipenv for virtual environment.
• Now install required python packages for our project.
• flask 

  pip install Flask
  

• flask-login

  pip install Flask-Login

• flask-SQLalchemy

  pip install Flask-SQLAlchemy
  

• Now create a file models.py for database model.

from flask_sqlalchemy import SQLAlchemy
from werkzeug.security import generate_password_hash, check_password_hash
from flask_login import UserMixin
 
db = SQLAlchemy()
 
class UserModel(UserMixin, db.Model):
    __tablename__ = 'users'
 
    id = db.Column(db.Integer, primary_key=True)
    email = db.Column(db.String(80), unique=True)
    username = db.Column(db.String(100))
    password_hash = db.Column(db.String())
 
    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)

• In this, we are creating an email, username, and password field.
• Password field is has using werkzeug security library.
• In UserModel class, we created a set password method and check password methods.
• Now we have to initialize flask login extension in our app.
• So create a new file called auth.py and create these methods.

from flask_login import LoginManager

from models import UserModel
login = LoginManager()
 
@login.user_loader
def load_user(id):
    return UserModel.query.get(int(id))

• Create our main flask app file called main.py and configure the database.

from flask import Flask
  
app =Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///<db_name>.db'
app.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = False
  
app.run(host='localhost', port=5000)

• Adding login extension to our app.

from flask import Flask
from auth import login
 
app =Flask(__name__)
 
login.init_app(app)
 
app.run(host='localhost', port=5000)

• Create a method for login view.

@app.route('/login', methods = ['POST', 'GET'])
def login():
    if current_user.is_authenticated:
        return redirect('/blogs')
     
    if request.method == 'POST':
        email = request.form['email']
        user = UserModel.query.filter_by(email = email).first()
        if user is not None and user.check_password(request.form['password']):
            login_user(user)
            return redirect('/blogs')
     
    return render_template('login.html')

• Create a login.html file

<form action="" method ="POST">
    <p>email <input type ="email" name ="email" /></p>
    <p>password <input type ="password" name ="password" /></p>
    <p> submit <input type ="submit" value ="Submit" /></p>
</form>
 
<h3>Dont Have an account??</h3>
<h3><a href ="{{url_for('register') }}">Register Here</a></h3>

• Create a register method.

@app.route('/register', methods=['POST', 'GET'])
def register():
    if current_user.is_authenticated:
        return redirect('/blogs')
     
    if request.method == 'POST':
        email = request.form['email']
        username = request.form['username']
        password = request.form['password']
 
        if UserModel.query.filter_by(email=email):
            return ('Email already Present')
             
        user = UserModel(email=email, username=username)
        user.set_password(password)
        db.session.add(user)
        db.session.commit()
        return redirect('/login')
    return render_template('register.html')

• Create register.html file

<form action="" method ="POST">
    <p>email <input type ="email" name ="email" /></p>
    <p>Username <input type ="text" name ="username" /></p>
    <p>password <input type ="password" name ="password" /></p>
    <p> submit <input type ="submit" value ="Submit" /></p>
</form>
 
<h3>Already Have an Account?</h3><br>
<h3><a href ="{{url_for('login')}}">Login Here</a></h3>

• Create logout method

@app.route('/logout')
def logout():
    logout_user()
    return redirect('/blogs')

• All main.py file methods

from flask import Flask,render_template,request,redirect
from flask_login import login_required, current_user, login_user, logout_user
from models import UserModel,db,login

from auth import login

app = Flask(__name__)
app.secret_key = 'xyz'
 
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///data.db'
app.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = False
 
 
db.init_app(app)
login.init_app(app)
login.login_view = 'login'
 
@app.before_first_request
def create_all():
    db.create_all()

@app.route('/index')
@login_required
def index():
    return render_template('index.html')

@app.route('/login', methods = ['POST', 'GET'])
def login():
    if current_user.is_authenticated:
        return redirect('/index')
     
    if request.method == 'POST':
        email = request.form['email']
        user = UserModel.query.filter_by(email = email).first()
        if user is not None and user.check_password(request.form['password']):
            login_user(user)
            return redirect('/index')
     
    return render_template('login.html')
 
@app.route('/register', methods=['POST', 'GET'])
def register():
    if current_user.is_authenticated:
        return redirect('/index')
     
    if request.method == 'POST':
        email = request.form['email']
        username = request.form['username']
        password = request.form['password']
 
        if UserModel.query.filter_by(email=email).first():
            return ('Email already Present')
             
        user = UserModel(email=email, username=username)
        user.set_password(password)
        db.session.add(user)
        db.session.commit()
        return redirect('/login')
    return render_template('register.html')
 
 
@app.route('/logout')
def logout():
    logout_user()
    return redirect('/login')

• These are all methods to login register and logout in flask login.
• Also, there are autentication models.

That's all thanks for reading 😁