Part of setting up the database is handling connecting and disconnecting from our database responsibly. To do that, we use the before_request and after_request decorators.

The g object that Flask gives us helps us make different things global. We’ll use it to make our database connection and our current user available everywhere. Having a global database will make it a lot easier for us if we decide to build our app with a lot of different modules.

Flask Login is used to find the current user, or any user we’re looking for. To help with this process, we need to create a function that will return an instance of our user model; load_user(userID) that uses the login user_loader decorator.

[app.py]

from flask import Flask, g
from flask.ext.login import LoginManager

import models

DEBUG = True
PORT = 8000
HOST = '0.0.0.0'


app = Flask(__name__)
app.secret_key = 'jnkla@sdioa!sdjoo^paud&1293*hoads.ln10'


login_manager = LoginManager()
login_manager.init_app(app)
login_manager.login_view = 'login'

@login_manager.user_loader
def load_user(userID):
    try:
        models.User.get(models.User.id == userID)
    except models.DoesNotExist:
        return None


@app.before_request
def before_request():
    """Connect to the database before each request"""
    g.db = models.DATABASE
    g.db.connect()
    

@app.after_request
def after_request(response):
    """Close the database connection after each request"""
    g.db.close()
    return response


if __name__ == '__main__':
    models.initialize()
    models.User.create_user(
        username='basharghadanfar',
        email='10.tens@gmail.com',
        password='123456',
        admin=True
        )
    app.run(debug=DEBUG, port=PORT, host=HOST)

secret_key
Used whenever we need to use sessions for our users.

login_manager = LoginManager()
Creates an instance of LoginManager.

login_manager.init_app(app)
Sets up the login_manager for our app.

login_manager.view = ‘login’
Naming the login view – which we don’t have yet – to which we will redirect the users in case they’re not logged in.

@login_manager.user_loader
def load_user(userID):
The function that the login_manager will use whenever it needs to lookup a user.

models.User.id
Returns the primary key, which had been automatically retrieved and stored on the record / model instance.

models.DoesNotExist
This is an exception that comes from PeeWee – which we’ve imported – and is used when failing to return a record with certain values.

g.db.close()
Closes the global database.

models.User.create_user( … )
We used the create_user classmethod to create an admin/superuser instead of CRUD’s .create, because we will always want a user with an encrypted password.

If we were to run:

>>> python app.py

it would initialize our models by connecting to the database, then create the User model, close the connection, then create a superuser for us – in case a superuser doesn’t exist already, and finally run the app.