Flask is a very small framework for eveloping web apps.

Create the following directory structure:

routes.py
templates
static
- css
- img
- js
Readme.md Flask relies on Jinja2 templates. These look like:

{% extends "layout.html" %}

{% block content %}
  <main class="hero-section">
  </main>
{% endblock %}

routes.py contains the main dispatcher:

brush:python
from flask import Flask, render_template

app = Flask(__name__)

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

@app.route("/about")
def about():
  return render_template("about.html")

if __name__ == "__main__":
  app.run(debug=True)

To install flask it is best to use a VirtualEnv. Download from the web and create a new virtual environment:

python virtualenv.py my_ve

To activate or deactivate th virtual environment:

source my_ve/bin/activate
source my_ve/bin/deactivate

To install flask in the VE:

pip install flask

To deploy to heroku:

Install heroku CLI
Install gunicorn web server

pip install gunicorn

Create a requirements.txt

pip freeze >requirements.txt

Create a Procfile to tell Heroku to run flask in gunicorn

web:gunicorn routes:app

Create a heroku app

heroku create

We can now push to Heroku git repo

git push heroku master

Open in browser with

heroku open

Database

Using the Flask SQLAlchemy extension:

pip install flask-sqlalchemy

and add this line to routes.py

app.config["SQLALCHEMY_DATABASE_URI"] = 'postgresql://localhost/db_name'

Create a models.py:

from flask.ext.sqlalchemy import SQLAlchemy

db = SQLAlchemy()

class User(db.Model):
  __tablename__ = 'users'
  uid = db.Column(db.Integer, primary_key = True)
  firstname = db.Column(db.String(100))
  lastname = db.Column(db.String(100))
  email = db.Column(db.String(120), unique=True)
  pwdhash = db.Column(db.String(54))

  def __init__(self, firstname, lastname, email, password):
    self.firstname = firstname.title()
    self.lastname = lastname.title()
    self.email = email.lower()
    self.set_password(password)

The main routes.py needs to initialize the db object:

brush:python
from models import db

db.init_app(app)

Based on "Learning Flask" course at lynda.com, git repo

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Simple web app development with Flask

Database