Flask Implementation with SQL Alchemy & PostgreSQL

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If you want to create a lightweight and fast web app, Flask is the best solution. Flask is written in Python and one of the most widely used Python web frameworks for start-ups, and is becoming commonly accepted as the perfect tool for quick and simple solutions in most businesses. At its core, it provides a set of powerful libraries.

What Will I Learn?

Combine python with Flask
Implement Login Flask-SQLAlchemy with PostgreSQL

Requirements

Install Python3.6
Install pip
Install virtualenv
Install Flask
Install PostgreSQL
Install Flask SQLALchemy
Browser(Chrome, IE, FireFox)

Difficulty

Basic

Tutorial Contents

Flask is written in Python so we have to install python. Instructions for installing Python can be found here.
If we want to know python version installed just type:
python

The first thing to do is create the environment in our folder to isolate python systems and third party packages. Open command line then locate the python version file in system. After you found the version, type:
python -m venv E:\Learn\Flask\flask_bootstrap\venv

We have to enable virtual environment that we created in our previous folder:
E:\Learn\Flask\flask_bootstrap>cd venv/Scripts

and then type activate

Install flask with pip with command
pip install flask
The goal is to install the project flask package in the environment we have created in our folder

Install flask_sqlalchemy with the command
pip install flask_sqlalchemy
The purpose is installing it as an extension of flask to support SQLAlchemy in application

Install psycopg2 as PostgreSQL database adapter for the Python programming language. Type:
pip install psycopg2

Create a new file in the directory flaskbootstrap named app.py. Enter the following code:

from flask import Flask 
from flask_sqlalchemy import SQLAlchemy
from flask import render_template,request, redirect, url_for
app = Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI'] = 'postgresql://postgres:Amazing@localhost/flaskbootstrap'
app.debug = True
db = SQLAlchemy(app)
class User(db.Model):
        id = db.Column(db.Integer, primary_key=True)
        username = db.Column(db.String(80), unique=True)
        email = db.Column(db.String(120), unique=True)
        def __init__(self, username, email):
                self.username = username
                self.email = email
        def __repr__(self):
                return '<User %r>' % self.username
@app.route('/')
def index():
        myUser = User.query.all()
	oneItem = User.query.filter_by(username="test1").first()
        return render_template('add_user.html', myUser=myUser, oneItem=oneItem)
@app.route('/post_user', methods=['POST'])
def post_user():
        user = User(request.form['username'], request.form['email'])
        db.session.add(user)
        db.session.commit()
        return redirect(url_for('index'))
if __name__ == "__main__":
        app.run()

Create a directory static and templates in flask_bootsrap . After that create a new file in templates name add_user.html Enter the following code:

<!DOCTYPE html>
<html>
<head>
	<title></title>
	<meta charset="utf-8">
</head>
<body>
	<form method="post" action="/post_user">
		<label>Username:</label>
		<input id="username" name="username" type="text" />
		<label>Email:</label>
		<input id="email" name="email" type="text" />
		<input type="submit" />
	</form>
	{% for user in myUser %}
		<li>{{ user.id }} {{ user.username }} - {{ user.email }}</li>
	{% endfor %}
</body>
</html>

if all is installed, you can type typing python app.py command

Open your favorite web-browser and navigate to the URL displayed http://localhost:5000

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