setup.rst

Step 2: Application Setup Code

Now that we have the schema in place we can create the application module. Let's call it flaskr.py inside the flaskr folder. For starters we will add the imports we will need as well as the config section. For small applications it's a possibility to drop the configuration directly into the module which we will be doing here. However a cleaner solution would be to create a separate .ini or .py file and load that or import the values from there.

# all the imports
import sqlite3
from flask import Flask, request, session, g, redirect, url_for, \
     abort, render_template, flash

# configuration
DATABASE = '/tmp/flaskr.db'
DEBUG = True
SECRET_KEY = 'development key'
USERNAME = 'admin'
PASSWORD = 'default'

Next we can create our actual application and initialize it with the config:

# create our little application :)
app = Flask(__name__)
app.secret_key = SECRET_KEY
app.debug = DEBUG

The secret_key is needed to keep the client-side sessions secure. Choose that key wisely and as hard to guess and complex as possible. The debug flag enables or disables the interactive debugger. Never leave debug mode activated in a production system because it will allow users to executed code on the server!

We also add a method to easily connect to the database specified. That can be used to open a connection on request and also from the interactive Python shell or a script. This will come in handy later

def connect_db():
    return sqlite3.connect(DATABASE)

Finally we just add a line to the bottom of the file that fires up the server if we run that file as standalone application:

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

With that out of the way you should be able to start up the application without problems. When you head over to the server you will get an 404 page not found error because we don't have any views yet. But we will focus on that a little later. First we should get the database working.

Externally Visible Server

Want your server to be publically available? Check out the externally visible server <public-server> section for more information.