Large app how to

This document is an attempt to describe the first step of a large project structure with flask and some basic modules:

• SQLAlchemy
• WTF (What The Form)

Please feel free to fix and add you own tips.

Installation

Flask

[http://flask.pocoo.org/docs/installation/](Flask Installation) I recommend using virtual env: easy and allow multiple environment on the same machine and doesn't even require you to have super user right on the machine (as the libs are localy installed).

Flask-SQLAlchemy

SQL provide an easy and advanced way to serialize your object to different type of relational database. In your virutal env, install SQLAlchemy from pip:

pip install flask-sqlalchemy

[http://packages.python.org/Flask-SQLAlchemy/](More here about SQL Alchemy flask package)

Flask-WTF

WTF (What the Form) Provides a easy way to handle user's data submission.

pip install Flask-WTF

[http://packages.python.org/Flask-WTF/](More here about What The Form flask package)

Overview

Ok, so from now, we should have all the libs ready. Here the folder structures:

config.py  
run.py  
shell.py  
app.db
app/__init__.py
app/constants.py

For every module (or sub app... ) well have this file structure (here for the users module)

app/users/__init__.py
app/users/views.py
app/users/forms.py
app/users/constants.py
app/users/models.py
app/users/decorators.py
app/templates/users/login.html
app/templates/users/register.html
...

We'll create 4 modules, a user module (manage user's registration, login, password lost, profile edit and maybe Third party Login/Registration) an email sub module intended to be used by a queuing server, and a post and comments modules

Config

run.py will be used to launch the web server.

from tol import app
app.run(debug=True)

shell.py will allow you to get a console and enter commands within your flask environment. Maybe not as nice as debugging with pdb, but always usefull (when you will initialize your database)

#!/usr/bin/env python
import os
import readline
from pprint import pprint

from flask import *
from app import *

os.environ['PYTHONINSPECT'] = 'True'

config.py will be storing all the module configurations. Here, the database is setup to use SQLite, because it's a very convenient dev env database. Most likely config.py won't be a part of your repository and will be different on your test and production servers.

import os
_basedir = os.path.abspath(os.path.dirname(__file__))

DEBUG = False

ADMINS = frozenset(['youremail@yourdomain.com'])
SECRET_KEY = 'SecretKeyForSessionSigning'

SQLALCHEMY_DATABASE_URI = 'sqlite:///' + os.path.join(_basedir, 'app.db')
DATABASE_CONNECT_OPTIONS = {}

THREADS_PER_PAGE = 8

CSRF_ENABLED=True
CSRF_SESSION_KEY="somethingimpossibletoguess"

RECAPTCHA_USE_SSL = False
RECAPTCHA_PUBLIC_KEY = 'blahblahblahblahblahblahblahblahblah'
RECAPTCHA_PRIVATE_KEY = 'blahblahblahblahblahblahprivate'
RECAPTCHA_OPTIONS = {'theme': 'white'}

del os

• _basedir is a trick for you to get the folder where the script runs
• DEBUG indicate that it is a dev environment, you'll get the very helpful error page from flask when an error occur.
• SECRET_KEY will be use to sign the cookies. Change it and all your user will have to login again.
• ADMINS
• SQLALCHEMY_DATABASE_URI and DATABASE_CONNECT_OPTIONS are SQLAlchemy connection options (hard to guess )
• THREAD_PAGE my understanding was 2/core... might be wrong :)
• CSRF_ENABLED CSRF_SESSION_KEY is protecting against form post fraud
• WTF comes with REPCAPTCHA field ready to use... just need to go to repcatcha website and get your public and private key.