Authenticating users

We can now look at how to authenticate users. This is a very simple process:

1. Retrieve the user we want to authenticate from the database.
2. Perform a bcrypt.checkpw giving it the attempted password and the password hash of the user.
3. Raise an exception if the result is False.
4. Return the user if it's True.

Retrieving users from the database

Starting with the first point, we will need to add a new dependency method, get, which returns the user, given the email, if it exists.

First, add a new exception class in users.py:

class UserNotFound(Exception): 
    pass 

This is what we will raise in the event of the user not being found. Now we will update our imports to include the following:

from sqlalchemy.orm.exc import NoResultFound 

NoResultFound, as the name implies, is raised by SQLAlchemy when a requested object is not found in the database. Now we can add a new method to our UserWrapper class:

def get(self, email): 
    query = self.session.query(User) # ① 
 
    try: 
        user...