MongoDB is fairly easy-to-use nosql database and the python module mongoengine makes the life even better to work with mongodb from python.
MongoDB binaries are available on the website, but be careful to choose between 32/64 bit versions. When in doubt use $uname -m.
mongoengine can be installed via easy_install, but on importing that it showed me that multiprocessing module was necessary. I had to get build-essentials module and upgrade libc6 on my Ubuntu to get multiprocessing installed.
So, once django, mongodb and mongoengine are installed, let's see how we can make a simple app that takes a comment, commenter's name, stores them and displays back 4 per page.
As for any django app, first make a project with
$ django-admin.py startproject django-mongodb
$ cd django-mongodb
Edit settings.py to remove all the default INSTALLED_APPS and configure database settings. Here comes the not so straight-forward thing to do. As per intuition, one tends to keep ENGINE as django.db.backends.mongodb in DATABASES and expects things to work. But there is no such thing as mongodb or mongo in django.db.backends. The mongoengine website says not to bother about the DATABASES dict at all and having mongoengine.connect(db_name) somewhere in the settings.py will work. With that in place, django complaints that you haven't set the database and hence can't do syncdb successfully.
Now, what's the solution? Well, just keep django.db.backends.sqlite3 as the engine with some dummy name and do the mongoengine.connect. Django no more complains when you run syncdb, in fact it creates both the sqlite database (empty) and mongodb database, provided you have mongod running up and sqlite3 installed.
Once the db connections are done, add comments in INSTALLED_APPS and run
$ python manage.py startapp comments
That creates comments dir in cwd which has views.py, models.py in it. Usually in models.py we write classes that extend from django.db.models.Model and django figures out how to create db schema for them. With mongoengine, mongoengine.Document extends Model and it suffices for us to extend our models from Document. Writing urls and views are the regular tasks as in any other django app. For the POST requests, django uses csrf_token as a security measure against CSRF attacks - so, one shouldn't miss that out in sending post request as well as in the template. Lastly, django's Paginator module comes very handy for pagination. Some basic javascript form validation makes it work better and it comes for free with jquery.validate.js, which works like a charm. That's it - we're ready with the comments app!
Now, for the deployment, we have fabulous Fabric. The time spent with fabric pays us very quickly - when you deploy on a clean slate and test you don't need to remember the sequence of commands or the args to them. What a savior!