login.html

# this goes under ./templates

{% block content %}
    <h1>Sign In</h1>
    <form action="" method="post" novalidate>
        {{ form.hidden_tag() }}
        <p>
            {{ form.username.label }}<br>
            {{ form.username(size=32) }}
        </p>
        <p>
            {{ form.password.label }}<br>
            {{ form.password(size=32) }}
        </p>
        <p>{{ form.remember_me() }} {{ form.remember_me.label }}</p>
        <p>{{ form.submit() }}</p>
    </form>
{% endblock %}

rest_server.py

# rest server with a database

from flask import Flask, jsonify, request
from flask_sqlalchemy import SQLAlchemy


app = Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///examen.db'
app.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = True

db = SQLAlchemy(app)


class Data(db.Model):

    __table_args__ = {'sqlite_autoincrement': True}

    id = db.Column(db.Integer, unique=True, nullable=False, primary_key=True)
    data = db.Column(db.String(80), default="some_default_data")

    @property
    def serialize(self):
        return {
            'id': int(self.id),
            'data': str(self.data)
        }


@app.route('/api/v1/data', methods=['POST'])
def add_user():
    try:
        content = request.json

        user = Data(
            data=content['data']
        )

        db.session.add(user)
        db.session.commit()

        return jsonify({
            'id': user.id,
            'data': user.data
        }), 200
    except Exception as e:
        return jsonify({
            'error': str(e)
        }), 404


@app.route('/api/v1/data', methods=['GET'])
def get_users():
    try:
        data_list = Data.query.all()
        return jsonify([u.serialize for u in data_list])
    except Exception as e:
        return jsonify({
            'error': str(e)
        }), 404


if __name__ == '__main__':
    db.drop_all()
    db.create_all()

    app.run(debug=True)

template_example.py

from flask_wtf import FlaskForm
from flask import (
    Flask,
    render_template,
    flash,
    redirect,
)
from wtforms import (
    StringField,
    PasswordField,
    BooleanField,
    SubmitField
)
from wtforms.validators import DataRequired
import os


SECRET_KEY = os.urandom(32)
app = Flask(__name__, template_folder='templates')
app.config['SECRET_KEY'] = SECRET_KEY


class LoginForm(FlaskForm):
    username = StringField('Username', validators=[DataRequired()])
    password = PasswordField('Password', validators=[DataRequired()])
    remember_me = BooleanField('Remember Me')
    submit = SubmitField('Sign In')


@app.route('/index', methods=['GET'])
def index():
    return 'index page'


@app.route('/login', methods=['GET', 'POST'])
def login():
    form = LoginForm()
    if form.validate_on_submit():
        flash('Login requested for user {}, remember_me={}'.format(
            form.username.data, form.remember_me.data))
        return redirect('/index')
    return render_template('login.html', title='Login', form=form)


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