One of the tasks that seems to come up every single project we do, is changing the auth backend to accept email addresses. Since it’s such a common task for us, it can’t be that rare to want this functionality. So, here’s a quick and simply backend which accomplishes this, using the built-in django.contrib.auth module.

from django.conf import settings
from django.contrib.auth.models import User

class EmailOrUsernameModelBackend(object):
    def authenticate(self, username=None, password=None):
        if '@' in username:
            kwargs = {'email': username}
        else:
            kwargs = {'username': username}
        try:
            user = User.objects.get(**kwargs)
            if user.check_password(password):
                return user
        except User.DoesNotExist:
            return None

    def get_user(self, user_id):
        try:
            return User.objects.get(pk=user_id)
        except User.DoesNotExist:
            return None

Then in your settings:

AUTHENTICATION_BACKENDS = (
    'myproject.accounts.backends.EmailOrUsernameModelBackend',
    'django.contrib.auth.backends.ModelBackend'
)