Tag: sqlalchemy

This whole tutorial describes in depth how to create a React website with Python. You must have Eclipse installed before you continue. If you have it already installed and configured you can continue on. Note that you should probably have HTML Editor and TypeScript IDE installed for Eclipse.

FYI: I am using Windows at the moment for this tutorial but you can substitute Ubuntu in if you so chose.

We will require Postgres 9.4, nodejs before you continue. You can get Nodejs from here. You can get Postgres 9.4 from here.

In this tutorial we use Flask. If you are not familiar with it go here. Flask is a lightweight Python web framework based on Werkzeug and Jinja 2.

Folder Structure:

• You will need to create a folder called “testApp”.
• Inside testApp create the following:
  • folder: app
    • file: models.py
    • file: __init__.py
    • folder: auth
      • file: __init__.py
      • file: views.py
    • folder: home
      • file: __init__.py
      • file: views.py
      • folder: js
        • file: home.jsx
    • folder: templates
      • file: base.html
      • file: login.html
      • file: register.html
  • file: config.py
  • file: requirements.txt
  • file: webpack.config.js
  • file: run.py
  • folder: instance
    • file: config.py
  • folder: static
    • folder: common
      • folder: css
        • file: base.css
    • file: manifest.json
  • .babelrc

Install Python Packages:

Open cmd/terminal and navigate into your testApp folder and run the following commands.

pip install flask-sqlalchemy && pip freeze > requirements.txt
pip install flask-login && pip freeze > requirements.txt
pip install flask-migrate && pip freeze > requirements.txt
pip install psycopg2 && pip freeze > requirements.txt
pip install flask-Webpack && pip freeze > requirements.txt
pip install Flask-WTF && pip freeze > requirements.txt
pip install flask-bootstrap && pip freeze > requirements.txt

Couple things to note:

• The “&& pip freeze > requirements.txt” saves the install in requirements.txt.
• flask-migrate: database migrations package
• flask-sqlalchemy: model engine for your database.
• flask-login: provides user session management for Flask
• psycopg2: Postgres driver
• flask-Webpack: A Flask extension to manage assets with Webpack
• flask-WTF: flask form validation
• flask-bootstrap: An extension that includes Bootstrap in your project, without any boilerplate code

Routing:

For the purpose of this example we are using the basic Flask implementation. IE: @home.route(‘/’). However if you want to do a more advanced routing do Resource.

Database:

Open PgAdmin III and create yourself a database called “testApp”. Also create a user with password granting access to testApp database. Permission as you see fit. Don’t forget to write down your password :).

Setup Config.py:

Read here for SqlAlchemy configruation options. DEBUG is for flask debugging.

class Config(object):
    """
    This is the shared common configurations
    """

    # Put any configurations here that are common across all environments

class DevelopmentConfig(Config):
    """
    This is the development configurations
    """
    
    DEBUG = True
    SQLALCHEMY_ECHO = True #Display queries to console

class ProductionConfig(Config):
    """
    This is the production configurations
    """
    DEBUG = False
    SQLALCHEMY_ECHO = False #Do not Display queries to console

app_config = {
    'development': DevelopmentConfig,
    'production': ProductionConfig
}

Things to Note:

Notice how we don’t have any database connections in this config.py. That is because we really shouldn’t checkin to source control our database connection strings, etc.

Setup instance config.py:

We open the file config.py inside our “instance” folder and add this line only.

SQLALCHEMY_DATABASE_URI = "postgresql://##USER##:##PASSWORD##@##HOST##/testApp"

Setup __init__.py in “app” folder:

from flask import Flask
from flask_sqlalchemy import SQLAlchemy
from flask_login import LoginManager
from flask_migrate import Migrate
from flask_bootstrap import Bootstrap
import os

#Importing from the config.py
from config import app_config

# db variable initialization
db = SQLAlchemy()

#The flask login manager
login_manager = LoginManager()

webpack = Webpack()

def create_app(config_name):
    #This will be either "development" or "production" mapped to what we write in the config.py application
    #static_folder is where the static folder will be located
    app = Flask(__name__, instance_relative_config=True, static_folder=os.path.join(os.getcwd(), "static"))
    print('Running in %s' % (config_name))
    app.config.from_object(app_config[config_name])
    app.config.from_pyfile('config.py')
    #You need a secret key to be able to utilise the database connection
    app.secret_key = 'Awesome App'
    Bootstrap(app)
    db.init_app(app)
    #This will make it so our chunked js files are able to be loaded on the template
    app.config.update({'WEBPACK_MANIFEST_PATH': '../manifest.json'})
    webpack.init_app(app)

    #if a user tries to access a page that they are not authorized to, it will redirect to the specified view and display the specified message.
    login_manager.init_app(app)
    login_manager.login_message = "You must be logged in to access this page."
    #auth.login is not the route but actually the class path.
    login_manager.login_view = "auth.login"
    
    #This let's us do our migrations
    migrate = Migrate(app, db)

    #Bring in our new tables
    from app import models

    #Our blueprints for our app

    #This is how you get authenticated
    from .auth import auth as auth_blueprint
    app.register_blueprint(auth_blueprint)
	
    #Bring in the home module
    from .home import home as home_blueprint
    app.register_blueprint(home_blueprint)

    return app

Environment Variable Setup:

Flask has two environment variables that you can set which point to the environment to use and the run.py file. These are FLASK_CONFIG and FLASK_APP. I set my environment to “development” and the app to use “run.py”. Notice that “development” maps to the key value pair in config.py.

Setup run.py:

Notice how we utilise the FLASK_CONFIG from the environment variables to setup our environment and grab the right config class.

import os #We need this to get the OS ENV VARIABLE 'FLASK_CONFIG'

#You are going to import the create_app from the __init__.py file
from app import create_app

#In our environment variables we create "FLASK_CONFIG" and set our value either development or production
config_name = os.getenv('FLASK_CONFIG')
app = create_app(config_name)

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

Now the fun really starts!!!

Setup models.py:

We setup our User model ensuring security of our password. Later on I will show you what happens with flask-migrate.

from flask_login import UserMixin
from werkzeug.security import generate_password_hash, check_password_hash

from app import db

class User(UserMixin, db.Model):
    """
    Create an Users table
    """

    # Ensures table will be named in plural and not in singular
    # as is the name of the model
    __tablename__ = 'users'

    id = db.Column(db.Integer, primary_key=True)
    email = db.Column(db.String(60), index=True, unique=True)
    username = db.Column(db.String(60), index=True, unique=True)
    first_name = db.Column(db.String(60), index=True)
    last_name = db.Column(db.String(60), index=True)
    password_hash = db.Column(db.String(128))

    @property
    def password(self):
        """
        Prevent pasword from being accessed
        """
        raise AttributeError('password is not a readable attribute.')

    @password.setter
    def password(self, password):
        """
        Set password to a hashed password
        """
        self.password_hash = generate_password_hash(password)

    def verify_password(self, password):
        """
        Check if hashed password matches actual password
        """
        return check_password_hash(self.password_hash, password)

    def __repr__(self):
        return ''.format(self.username)

Generate User Table:

Using flask-migrate we can now auto generate our User table into Postgres testApp database.

1. Run “flask db init” to create our migration repository
   1. A “migrations” folder is created automatically.
2. Run “flask db migrate”
   1. This generates the migration script
3. Run “flask db upgrade”
   1. This creates the missing migrations into the database. AKA the users table.
   2. You will notice another table also got created “alembic_version”. This is how it stores the version it is at.
4. Confirm that the db was migrated successfully.

Create Our Templates:

We use the base.html file for our react pages using the “app” id on the div. The login.html is for our login form and register.html is to register a new user. You can use the base.css file in the static/common/css folder to style it how you want. I recommend using flex.

base.html:

<!DOCTYPE html>
{% import "bootstrap/utils.html" as utils %}
{% import "bootstrap/wtf.html" as wtf %}
{% extends "bootstrap/base.html" %}
<html>
	<head>
		{% block head %}
		{{ super() }}
		<title>{{title}}</title>
		<link rel="stylesheet" type="text/css" href={{ url_for("static", filename="common/css/base.css") }} />
		{% endblock %}
	</head>
	{% block content %}
	<div class="container-app">
		<div class="container-header">Team Link</div>
	    <div class="container-body" id="app"></div>
	    <script type="text/javascript" src={{ asset_url_for(script_name) }}></script>
	</div>
	{% endblock %}
</html>

login.html:

<!DOCTYPE html>
{% import "bootstrap/utils.html" as utils %}
{% import "bootstrap/wtf.html" as wtf %}
{% extends "bootstrap/base.html" %}
<html>
	<head>
		{% block head %}
		{{ super() }}
		<title>{{title}}</title>
		<link rel="stylesheet" type="text/css" href={{ url_for("static", filename="common/css/base.css") }} />
		{% endblock %}
	</head>
	{% block content %}
	<div class="container-app">
		<div class="container-header">My Awesome App</div>
	    <div class="container-body" id="app">
			<div class="panel panel-default">
				<div class="panel-heading">
					<h3 class="panel-title">Login</h3>
				</div>
				<div class="panel-body">
					{{ wtf.quick_form(form) }}
				</div>	    
				{{ utils.flashed_messages() }}
				Click here to <a href="/register">register</a>
			</div>
		</div>
	</div>
	{% endblock %}
</html>

register.html

<!DOCTYPE html>
{% import "bootstrap/utils.html" as utils %}
{% import "bootstrap/wtf.html" as wtf %}
{% extends "bootstrap/base.html" %}
<html>
	<head>
		{% block head %}
		{{ super() }}
		<title>{{title}}</title>
		<link rel="stylesheet" type="text/css" href={{ url_for("static", filename="common/css/base.css") }} />
		{% endblock %}
	</head>
	{% block content %}
	<div class="container-app">
		<div class="container-header">Team Link</div>
	    <div class="container-body" id="app">
			<div class="panel panel-default">
				<div class="panel-heading">
					<h3 class="panel-title">Register</h3>
				</div>
				<div class="panel-body">
    				{{ wtf.quick_form(form) }}
				</div>	    
				{{ utils.flashed_messages() }}
				Click here to <a href="login">login</a>
			</div>
		</div>
	</div>
	{% endblock %}
</html>

Setup home __init__.py:

This creates the blueprint that we have in app.__init__.py.

from flask import Blueprint

home = Blueprint('home', __name__)

#This is the views.py from the home directory.
from . import views

Setup home views.py:

@login_required let’s flask know that you need to be logged in to get to this page. Don’t forget to see “render_template” method. How it has “script_name” in it and it uses base.html template. “script_name” was utilised in base.html. It brings in our js file for us on each page we go to.

from flask import render_template
from flask_login import login_required

#This is our blueprint we setup in __init__.py
from . import home

@home.route('/')
@login_required
def homepage():
    """
    Render the homepage template on the / route
    """
    return render_template('base.html', script_name='home.js', title="Welcome")

Setup React home JSX file:

React uses jsx files. So in my home directory I have a js folder and inside that we have our home.jsx file. Let’s set that up to something really basic. Remember above I said in the “render_template” we use the div id “app”. The ReactDOM will put our class in that spot. I will show you later how that is done.

var React = require("react");
var ReactDOM = require("react-dom");
var createReactClass = require("create-react-class");

var Home = createReactClass({
	render: function() {
		return (<div>Hi</div>);
	}
});

ReactDOM.render(<Home />, document.getElementById("app"));

Node Init:

We need to go to our root directory testApp from command prompt and run the following in the exact order.

npm init
npm install react react-dom --save
npm install webpack webpack-dev-server --save
npm install --save-dev babel babel-core babel-loader babel-preset-es2015 babel-preset-react
npm install create-react-class --save
npm install bootstrap --save
npm install jquery --save
npm install clean-webpack-plugin --save-dev
npm install manifest-revision-webpack-plugin --save-dev
npm install sync-exec --save-dev
npm install uglifyjs-webpack-plugin --save-dev

Things to Note:

• npm init: Creates package.json file
• npm install –save: will save the install to package.json
• Each package install went into a new directory called “node_modules”.

Setup webpack.config.js:

We want to transition our jsx files to .js. Remember back in app.__init__.py we setup the static folder location. Checkout the “path” key below and now we know how it knows where it’s assets are going to be located. Our entry key value pair is the locations of each of our jsx files to create assets from. Then we have our loaders.

var path = require("path");
var webpack = require('webpack');
var ManifestRevisionPlugin = require('manifest-revision-webpack-plugin');
const CleanWebpackPlugin = require('clean-webpack-plugin');

module.exports = {
	entry: {
		"home": [path.resolve(__dirname, "./app/home/js/home.jsx")],
	},
	output: {
        path: path.join(__dirname, "static"),
		publicPath: "/static/",
		filename: "[name]-[hash].js"
	},
	plugins: [
                new CleanWebpackPlugin(["static/*.js", "static/manifest.json"], {root: __dirname, verbose: true, dry: false, exclude: ["base.css"]}),
		new ManifestRevisionPlugin(path.resolve(__dirname, "./manifest.json"), {rootAssetPath: './static', ignorePaths: ['./node_modules']}),
		new webpack.NoEmitOnErrorsPlugin(),
		new UglifyJsPlugin(),
		new webpack.optimize.AggressiveMergingPlugin(),
		new webpack.HotModuleReplacementPlugin()
	],
	module: {
		loaders: [
			{
				test: /\.jsx?$/,
				exclude: /(node_modules)/,
				loader: 'babel-loader',
				query: {
					presets: ['react','es2015']
				}
			}
		]
	}
};

.babelrc

Set the following in your file at the root directory.

{
 "presets": [ "es2015", "react" ]
}

Let’s Test Node & Webpack:

Open command prompt and navigate to our testApp folder and run “webpack”. You will notice that a “static” folder is created in our root directory. In it we will now see “home.js” file. Remember back above we set __init__.py static folder and in home.views.py file we said in render_template script_name “home.js”. This is how it all maps together.

Setup auth __init__.py:

This creates the blueprint that we have in app.__init__.py.

from flask import Blueprint

auth = Blueprint('auth', __name__)

#This is the views.py from the auth directory.
from . import views

Setup auth views.py:

from flask import flash, redirect, render_template, url_for
from flask_login import login_required, login_user, logout_user
from flask_wtf import FlaskForm
from wtforms import PasswordField, StringField, SubmitField, ValidationError
from wtforms.validators import DataRequired, Email, EqualTo
from .. import db, login_manager
from ..models import User

from . import auth

class RegistrationForm(FlaskForm):
    """
    Form for users to create new account
    """
    email = StringField('Email', validators=[DataRequired(), Email()])
    username = StringField('Username', validators=[DataRequired()])
    first_name = StringField('First Name', validators=[DataRequired()])
    last_name = StringField('Last Name', validators=[DataRequired()])
    password = PasswordField('Password', validators=[
                                        DataRequired(),
                                        EqualTo('confirm_password')
                                        ])
    confirm_password = PasswordField('Confirm Password')
    submit = SubmitField('Register')

    def validate_email(self, field):
        if User.query.filter_by(email=field.data).first():
            raise ValidationError('Email is already in use.')

    def validate_username(self, field):
        if User.query.filter_by(username=field.data).first():
            raise ValidationError('Username is already in use.')

class LoginForm(FlaskForm):
    """
    Form for users to login
    """
    email = StringField('Email', validators=[DataRequired(), Email()])
    password = PasswordField('Password', validators=[DataRequired()])
    submit = SubmitField('Login')

@login_manager.user_loader
def load_user(id):
    #This is the how we locate the user in our testApp database
    return User.query.get(int(id))

@auth.route('/register', methods=['GET', 'POST'])
def register():
    form = RegistrationForm()
    if form.validate_on_submit():
        user = User(email=form.email.data,
                            username=form.username.data,
                            first_name=form.first_name.data,
                            last_name=form.last_name.data,
                            password=form.password.data)

        # add user to the database
        db.session.add(user)
        db.session.commit()
        flash('You have successfully registered! You may now login.')

        # redirect to the login page
        return redirect(url_for('auth.login'))

    # load registration template
    return render_template('register.html', form=form, title='Register')

@auth.route('/login', methods=['GET', 'POST'])
def login():
    form = LoginForm()
    if form.validate_on_submit():
        # check whether user exists in the database and whether
        # the password entered matches the password in the database
        user = User.query.filter_by(email=form.email.data).first()
        if user is not None and user.verify_password(
                form.password.data):
            # log user in
            login_user(user)

            # redirect to the dashboard page after login
            return redirect("/")

        # when login details are incorrect
        else:
            flash('Invalid email or password.')

    # load login template
    return render_template('login.html', form=form, title='Login')

@auth.route('/logout')
@login_required
def logout():
    """
    Handle requests to the /logout route
    Log an user out through the logout link
    """
    logout_user()
    flash('You have successfully been logged out.')

    # redirect to the login page
    return redirect(url_for('auth.login'))

Let’s Run our App:

Open command prompt navigate to our testApp folder and run “flask run”. If no mistakes were made you should now be able to navigate to our site. http://localhost:5000.

 

Resources:

In learning how to incorporate flask into python I used the following part one only tutorial as a guide. Very helpful.