Eighteen months of Django

It's not a Python package in the sense that you might mean, but using virtualenv is absolutely fundamental to good Python development (at least the kind that lets you keep your sanity).

South is also exceptional; however, the developer recently ran a successful Kickstarter campaign dedicated to creating an improved version intended to be merged with Django itself, so that's something to watch for.

Django-CMS has proven invaluable for many of my projects and clients, though it's very heavy and more of a project-tacked-on-to-your-project than just a package. It's great to know, though, and very powerful.

django-registration can be useful if you're into full-on user profile usage, though many sites don't actually need this. There's a separate project that provides a set of default templates for this package, and it's almost more useful than django-registration itself.

livesettings is an outgrowth of django-cms that's pretty useful when you need what would otherwise be settings.py constants that can be modified at runtime without a deployment and server restart. Be careful, though, as overuse of this means you might have design issues.

feedparser is a very, very easy way to consume XML feeds.

If you want to parse something in a very user-friendly way, BeautifulSoup is hard to beat. If you're into the nitty gritty and/or need serious performance, lxml serves the same purpose but kicks far more ass.

If you need to interface with Amazon's AWS environments (EC2, S3, etc.), boto is a brilliant library.

These are more Python-in-general than Django-specific, but that's often a good thing.

However, for large web projects, Django beats it hands down. Doing similar work with Flask would require so much wheel-reinvention that it'd be hard to justify your time or your client's money when it's all built quite well already.

Of course it's not perfect, and it's not for everything. But it's a great general-purpose, medium-performance web framework. It becomes a pain on very high-traffic sites (perhaps more so than JVM-based solutions and on par with scaling Ruby frameworks), but if you use it in the right place and/or team up with systems people that know their stuff, it's a powerful tool for quickly building complex websites in a maintainable and intuitive way.

Of course this means you'll have to keep track of where the uploaded file is currently located, but if you ever want to scale to multiple web servers you'll need to do that anyway.

This doesn't make it better, but it also doesn't make it worse.