Py Flask.py

# basic 'hello world' server

    from flask import Flask
    app = Flask(__name__)
    
    @app.route('/')
    def hello_world():
        return 'Hello, World'
        
    #export environment variable via terminal:
    #   flask_server % export FLASK_APP=hello.py
    
    #start development server via terminal
    # flask run
    
    #to run the server from the IDE, add:
    
    if __name__ == "__main__":
        app.run()
    
    
# route with variable rules

    @app.route('/username/<name>')
    def greet(name):
        return f"Hello {name}!"
        
        
# alternative variable rules

    @app.route('/username')
    def greet():
        return f"Hello {request.args.get('name')}!"
        
# run in debug mode

    if __name__ == "__main__":
        app.run(debug=True)
        
        
# render html with render remplates
    #the html files need to be stored in a directory called "templates"
    #any linked files like images or css files need to be stored in the directory "static"

    from flask import Flask
    from flask import render_template
    
    app = Flask(__name__)
    
    @app.route('/')
    def home():
        return render_template('index.html')
        

# redirect
    ...
        return redirect(url_for('secrets',name="Dominik"))
    
    
# receive post request from HTML

    #html
    <form action="/login" method="post">
        <label>Name</label>
        <input type="text" placeholder="name" name="username">
        <label>Password</label>
        <input type="text" placeholder="password" name="password">
        <button type="submit">Ok</button>
    </form>
    
    #Python
    @app.route('/login', methods=["POST"])
    def receive_data():
        name = request.form["username"]
        password = request.form["password"]
        return f'Name: {name}, Password: {password}'
        
        

        
# downloads

    @app.route('/download')
    def download():
        return send_from_directory('static', filename="files/cheat_sheet.pdf", as_attachment=True)
        
        
        
# store password hash

    from werkzeug.security import generate_password_hash

    ...
        password=generate_password_hash(request.form.get('password'), method='pbkdf2:sha256', salt_length=8)
    ...
    

# Flask-Login and securing routes

    # https://flask-login.readthedocs.io/en/latest/#how-it-works
    
    from flask_login import UserMixin, login_user, LoginManager, login_required, current_user, logout_user
    
    app.config['SECRET_KEY'] = 'any-secret-key-you-choose'
    
    login_manager = LoginManager()
    login_manager.init_app(app)
    
    @login_manager.user_loader
    def load_user(user_id):
        return User.query.get(int(user_id)) # "User refers to a table in the FLASK Alchemy Database"
    
    @app.route('/login', methods=['GET', 'POST'])
    def login():
        if request.method == 'POST':
            email = request.form.get('email')
            password = request.form.get('password')
            user = User.query.filter_by(email=email).first()
            if check_password_hash(user.password, password):
                login_user(user)
                return redirect(url_for('secrets'))
    
        return render_template("login.html")
        
        
    @app.route('/secrets')
    @login_required. # secures the route
    def secrets():
        return render_template("secrets.html", name=current_user.name)
        
        
    @app.route('/logout')
    def logout():
        logout_user()
        return redirect(url_for('home'))
        
        
    # admin only route via custom decorator
    
        from functools import wraps
        
        def admin_only(f):
        @wraps(f)
        def decorated_function(*args,**kwargs):
            if ( not current_user.is_authenticated or current_user.id != 1 ):
                return abort(403)
            return f(*args,**kwargs)
        return decorated_function