Django Middleware that supports masquerading as another user without authentication. Requires views that will set the _masq_user session variable.

masquerade.py

from django.contrib import auth
from django.core.exceptions import ImproperlyConfigured
from django.utils.functional import SimpleLazyObject


def get_user(request):
    if request.session.has_key("_masq_user"):
        return request.session["_masq_user"]
    if not hasattr(request, '_cached_user'):
        request._cached_user = auth.get_user(request)
    return request._cached_user


class MaqueradeMiddleware(object):
    def process_request(self, request):
        assert hasattr(request, 'session'), "The Django authentication middleware requires session middleware to be installed. Edit your MIDDLEWARE_CLASSES setting to insert 'django.contrib.sessions.middleware.SessionMiddleware'."

        request.user = SimpleLazyObject(lambda: get_user(request))