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Can I use Django to make non-web python apps as a data scientist?

I'm a data scientist, and I make apps using python. Where I make a lot of connections with databases, build and deploy my code on the cloud and I use models training and visualization.
My question is:
Is Django useful for making non-web apps?
if not are they any other frameworks? (similar to spring-boot for java)
Best regards

Django is a web framework which comes with many preinstalled apps. This will make your application bulkier than it is required.
For your usecase, you need not to use any frameworks. Just code it in python and you can use the available library to perform db operations.
If you are deploying your app on the cloud, and want expose some endpoints to trigger any of your internal functions, go with Flask framework. It is a light weight micro web framework

I would contrast the first answer and say absolutely you can use Django with no intentions of building a front end. The ORM is so powerful and easy to use along with the out-of-the-box signaling system among many other features. In my opinion a little extra "bulk" is worth the tools you have at your disposal with it. And of course you always have the option to add the front end later if you like.

Web Frameworks with site style inbuilt

I hope this isn't knocked for being too general, but... I recently had occasion to learn web2py for a final year university project. In this subject teams of four had 8 weeks to design a web app. Ultimately i found that web2py was quite versatile, with it being very easy to get a site up and running fast, a lot of options (janrain etc) - but the end "style" result relied almost entirely on us.
Amongst the other teams, who used other frameworks (each team a different one on the whole), a few of the sites came out with a very slick polished look, without them having to spend much photoshop/css design time and effort. I got the impression that some frameworks are more "friendly" when it came to out of the box design elements (buttons, navigation options, widgets, base css etc) while others aren't.
I have a python (/C/java) background, and intend to learn PHP some point. What frameworks exist out there that provided a base for site design beyond the bare bones? And to emphasise, I have browsed the python page listing frameworks, i am more interested in the design aspect - even if just to see if my assumption was correct.

I'm not sure other frameworks are necessarily more "friendly" regarding design elements, as the client-side styling is really independent of the server-side framework. You can easily plug in any front-end boilerplate/framework to provide nicer styling, whichever server-side framework you are using. At least among Python frameworks, I think web2py is one of the few to provide any front-end scaffolding application (including some basic styling) at all. With most of the others, you're on your own.
That having been said, web2py will soon be releasing a new mobile-friendly scaffolding application based on Skeleton, with improved styling. Though you can just as easily use other front-end frameworks, such as Twitter Bootstrap, Foundation, HTML5Boilerplate, etc.
web2py also allows for the development and application of layout plugins to easily replace the app's styling. Some examples can be found here and here, and they are also available in the application wizard (demo).

I feel your pain. As a developer coming from the desktop world and doing some web development, I'm used to setting up the appearance of my application at the same time I select and arrange my user interface widgets.
You will just have to accept that browser based software does not work that way. You must separately learn CSS. Hopefully, you'll learn to like this method of specifying the appearance of the application but whether you do or not there really isn't any alternative to this approach in the browser.

So far what I've seen about Yii Framework (PHP) is that it can generate an initial nice Styled Web Application backbone, ready for you to work in it adding your functionality, DBs, User roles, etc. and of course all the freedom to define your own Look and Feel by defining HTML views, CSS, JS, etc.
I'm about to start learning and using a PHP Framework for my next project. I have never yet used a Framework but I have several years using PHP/MySQL.
For some weeks I have researched on PHP Frameworks and there are CakePHP, CodeIgniter, Zend, Yii, Kohana, etc. and I'm leaning to Yii even though CodeIgniter seems to have more followers I'm stubborn on checking out Yii because of the high praise is getting specially in its quality built and performance.
I wouldn't know how good the other PHP frameworks are on the "default visual style" area.

Your question seems too generic. I believe your problem is the template library more than the whole framwework.
Maybe this is what you need: http://beebole.com/pure/. This is a javascript template library that let's you render pure html/css templates without embedded python code (dinamic parts are feeded using json data). In this way you can just take a well designed static website and render them dinamic with whatever web framework you like.

Python/GAE social network / cms?

After much research, I've come up with a list of what I think might be the best way of putting together a Python based social network/cms, but have some questions about how some of these components fit together.
Before I ask about the particular components, here are some of the key features of the site to be built:
a modern almost desktop-like gui
future ability to host an advanced html5 sub-application (ex.http://www.lucidchart.com)
high scalability both for functionality and user load
user ability to password protect and permission manage content on per item/group basis
typical social network features
ability to build a scaled down mobile version in the future
Here's the list of tools I'm considering using:
Google App Engine
Python
Django
Pinax
Pyjamas
wxPython
And the questions:
Google App Engine -- this is an attempt to cut to the chase as many pieces of the puzzle seem to be in place.
Question: Am I limiting my options with this choice? Example: datastore not being relational? Should I wait
for SQL support under the Business version?
Python -- I considered 'drupal' at first, but in the end decided that being dependent on modules that may or
may not exist tomorrow + limitations of its templating system are a no-no. Learning its API, too, would be useless elsewhere
whereas Python seems like a swiss army knife of languages -- good for almost anything.
Question: v.2.5.2 is required by GAE, but python.org recommends 2.5.5. Which do I install?
Django -- v.0.96 is built into GAE. You seem to be able to upgrade it.
Questions: Any reason not to upgrade to the latest version? Ways to get around the lack of HTML5 support?
Pinax (http://pinaxproject.com) Rides on top of Django and appears to provide most of the social network functionality
anyone would want.
Question: Reasons NOT to use it? Alternatives?
Pyjamas and wxPython -- this is the part that gets a little confusing. The basic idea behind these is the ability
to build a GUI. I've considered Silverlight and Flash, before the GAE/Python route, but a few working versions of
HTML5 apps convinced me that enough of it ALREADY runs on the latest batch of browsers to chose the HTML5/Javascript
route instead.
Question: How do I extend/supplement Python/Django to build an app-like HTML5 interface? Are Pyjamas and wxPython
the way to go? Or should I change my thinking completely?
Answers to some/any of these questions would be of great help. Please excuse my ignorance if any of this doesn't make much sense.
My last venture into web programming was a decent sized LAMP website some 5-6 years ago. On the desktop side of things,
my programming experience boils down to very high level scripting languages that I keep on learning to accomplish very specific
tasks :)

As someone who has deployed a Django site to GAE, I can tell you that you are not going to reach the ideal solution. Django on GAE misses some of the best aspects of Django because the ORM doesn't work right. The best compromise may be to use Django-nonrel to add the features back in.
This introduces it's own problems though: because of the large number of files and memory used by a Django app you're code will be unloaded from memory quickly after the app becomes idle. That means that visitors will frequently hit an approximately 6 second delay on the first page view after the site's code has been unloaded from memory while GAE uncompresses the zipped modules. Once your site is busy this won't be a problem, but while your site is still young and unknown it will cause the appearance of performance problems. :-(
Second, I've also worked for a company that built a custom CMS and can tell you that the first 80% is pretty easy, especially with modern frameworks. However, the rest can be quite challenging. For example, user roles and custom content types are two challenging aspects. Therefore strongly consider standing on the backs of giants and finding a CMS or CMS framework that almost perfectly meets your needs and then extend it to do that extra bit you need.
So, that said, answering your points:
Yes, you're limiting your options but that may be OK. Most developers are more comfortable with the relational model than the nosql model. Therefore more open source software is built with it in mind. Also, GAE is a closed source platform which is also a deterrent to open source developers. App Engine Oil is a CMS framework that may suit you well and is optimized for App Engine. Also look at web2py which has support for GAE.
I've found myself to be extremely productive with Python. I used to write a lot of PHP now I find it ugly. That said, think about the total line count of code you'll have to write. If you can make Drupal work with high quality pre-made modules you may find yourself only needing 1/10th of the code. By the way, the trick with Drupal is to mainly use only high quality modules. Look at the history, make sure not to use development versions. Try to contact the authors on IRC. I'm not saying you should use Drupal but it is possible to have a reliable site with it (for example, whitehouse.gov)
You're in the classic GAE/Django problem. If you use 0.96 you get great performance but you miss a lot of the great 1.0+ features and you don't get the ORM and all of it's benefits. If you use a newer version of Django you get the performance/memory problems mentioned above.
I'm about to investigate pinax for my company. I've done a very cursor glance at it. I don't know if it has good support for non relational model backends. You'll probably need to look at django-nonrel. However know that you're going to be investing in relatively untried solutions here. A small percentage of Django users use Pinax and an even smaller percentage, if any, use it on a nonrelational backend. Therefore you're going to be in the highly experimental scenario you mentioned in point 2 above.
I can't offer personal experience on it. I've investigated pyjamas a few times. However I like writing HTML CSS and JS. I like to have control. I like progressive enhancement and knowing what users will see if they don't have the full capabilities. Also, I think any new app that doesn't explicitly address mobile clients is implicitly shooting themself in the foot. As many as 15% of Internet users only use the Internet via their smart phone. What kind of experience will they get with pyjamas?
You didn't mention this, but one thing I consider when choosing a platform is vendor lockin and portability. If you develop your solution for GAE and find that you're not able to do what you want, will you be able to port it to another solution elsewhere? How much work will it take? If you code heavily for GAE or make commitments to its architecture, you're stuck with it or with rewriting to move. Using Django or Web2py can help mitigate this.
That said, the big benefit of Python GAE is that you get to be very productive, see your results instantly, get hosting for free while your site is small and get excellent scalability. These are not small things. There is great value there.

Why use Django on Google App Engine?

When researching Google App Engine (GAE), it's clear that using Django is wildly popular for developing in Python on GAE. I've been scouring the web to find information on the costs and benefits of using Django, to find out why it's so popular. While I've been able to find a wide variety of sources on how to run Django on GAE and the various methods of doing so, I haven't found any comparative analysis on why Django is preferable to using the webapp framework provided by Google.
To be clear, it's immediately apparent why using Django on GAE is useful for developers with an existing skillset in Django (a majority of Python web developers, no doubt) or existing code in Django (where using GAE is more of a porting exercise). My team, however, is evaluating GAE for use on an all-new project and our existing experience is with TurboGears, not Django.
It's been quite difficult to determine why Django is beneficial to a development team when the BigTable libraries have replaced Django's ORM, sessions and authentication are necessarily changed, and Django's templating (if desirable) is available without using the entire Django stack.
Finally, it's clear that using Django does have the advantage of providing an "exit strategy" if we later wanted to move away from GAE and need a platform to target for the exodus.
I'd be extremely appreciative for help in pointing out why using Django is better than using webapp on GAE. I'm also completely inexperienced with Django, so elaboration on smaller features and/or conveniences that work on GAE are also valuable to me.

Django probably isn't the right choice for you, if you're sure that GAE is right for you. The strengths of the two technologies don't align very well - you completely lose a lot of Django's wonderful orm on GAE, and if you do use it, you write code that isn't really directly suitable to bigtable and the way GAE works.
The thing about GAE is that it gets the great scalability by forcing you to write code that scales easily from the ground up. You just can't do a number of things that scale poorly (of course, you can still write poorly scaling code, but you avoid some pitfalls). The tradeoff is that you really end up coding around the framework, if you use something like Django which is designed for a different environment.
If you see yourself ever leaving GAE for any reason, becoming invested in the infrastructure there is a problem for you. Coding for bigtable means that it will be harder to move to a different architecture (though the apache project is working to solve this for you with the HBase component of the Hadoop project). It would still be a lot of work to transition off of GAE.
What's the driving motivator behind using GAE, besides being a Google product, and a cool buzzword? Is there a reason that scaling using something like mediatemple's offering is unlikely to work well for you? Are you sure that the ways that GAE scales are right for your application? How does the cost compare to dedicated servers, if you're expecting to get to that performance realm? Can you solve your problem well using the tools GAE provides, as compared to a more traditional load-balanced server setup?
All this said, unless you absolutely positively need the borderline-ridiculous scaling that GAE offers, I'd personally suggest not letting that particular service structure your choice of framework. I like Django, so I'd say you should use it, but not on GAE.
Edit (June 2010):
As an update to this comment sometime later:
Google has announced sql-like capabilitys for GAE that aren't free, but will let you easily do things like run SQL-style commands to generate reports on your data.
Additionally, there are upcoming changes to the GAE query language which will allow complex queries in a far easier fashion. Look at the videos from Google I/O 2010.
Furthermore, there is work being done during the Summer of Code 2010 project which should bring no-sql support to django core, and by extension, make working with GAE significantly easier.
GAE is becoming more attractive as a hosting platform.
Edit (August 2011):
And Google just raised the cost to most users of the platform significantly by changing the pricing structure. The lockin problem has gotten better (if your application is big enough you can deploy the apache alternatives), but for most applications, running servers or VPS deployments is cheaper.
Very few people really have bigdata problems. "Oh my startup might scale someday" isn't a bigdata problem. Build stuff now and get it out the door using the standard tools.

We use django on our appengine instances mostly when we have to serve actual websites to the user. It has a great template engine, url routing and all the request/response/error handling built in. So even while we can't use the magic orm/admin stuff it has a lot going for it.
For api services we built something very simple on top of webob. It's far more lightweight because it doesn't need everything that django offers, and therefore a little quicker in some situations.

I've done lots of projects on GAE. Some in django, some in their normal framework.
For small things, I usually use their normal framework for simplicity and quickness. Like http://stdicon.com, http://yaml-online-parser.appspot.com/, or http://text-twist.appspot.com/.
For large things, I go with django to take advantage of all the nice middleware and plugins. Like http://metaward.com.
Basically my litmus test is Will this take me more than 2 weeks to write and be a REAL software project? If so, go with django for the addons.
It has the added benefit of, if your project is badly suited for BigTable then you quickly port off (like I did Is BigTable slow or am I dumb?)

I think all this answers are a bit obsolete.
Now you can use Google Cloud SQL
Django is a popular third-party Python web framework. When coupled
with Google Cloud SQL, all of its functionality can be fully supported
by applications running on App Engine. Support for using Google Cloud
SQL with Django is provided by a custom Django database backend which
wraps Django's MySQL backend.
https://cloud.google.com/python/django/appengine
one more fresh news is, that there is BETA support for PostgreSQL

I have experience using Django and not GAE. From my experiences with Django it was a very simplistic setup and the deployment process was incredibly easy in terms of web projects. Granted I had to learn Python to really get a good hold on things, but at the end of the day I would use it again on a project. This was almost 2 years ago before it reached 1.0 so I my knowledge is a bit outdated.
If you are worried about changing platforms, then this would be a better choice I suppose.

I cannot answer the question but you may want to look into web2py. It is similar to Django in many respects but its database abstraction layer works on GAE and supports most of the GAE functionality (not all but we try to catch up). In this way if GAE works for you great, if it does not, you can move your code to a different db (SQLite, MySQL, PostgreSQL, Oracle, MSSQL, FireBird, DB2, Informix, Ingres, and - soon - Sybase and MongoDB).

If you decide to run you app outside of GAE, you can still use Django. You won't really have that much luck with the GAE webapp

I am still very new to Google App engine development, but the interfaces Django provides do appear much nicer than the default. The benefits will depend on what you are using to run Django on the app engine. The Google App Engine Helper for Django allows you to use the full power of the Google App Engine with some Django functionality on the side.
Django non-rel attempts to provide as much of Django's power as possible, but running on the app-engine for possible extra scalability. In particular, it includes Django models (one of Django's core features), but this is a leaky abstraction due to the differences between relational databases and bigtable. There will most likely be tradeoffs in functionality and efficiency, as well as an increased number of bugs and quirks. Of course, this might be worth it in circumstances like those described in the question, but otherwise would strongly recommend using the helper at the start as then you have the option of moving towards either pure app-engine or Django non-rel later. Also, if you do switch to Django non-rel, your increased knowledge of how app engine works will be useful if the Django abstraction ever breaks - certainly much more useful than knowledge of the quirks/workarounds for Django non-rel if you swap the other way.

Understanding Zope internals, from Django eyes

I am a newbie to zope and I previously worked on Django for about 2.5 years. So when I first jumped into Zope(v2) (only because my new company is using it since 7 years), I faced these questions. Please help me in understanding them.
What is the "real" purpose of zodb as such? I know what it does, but tell me one great thing that zodb does and a framework like Django (which doesn't have zodb) misses.
Update: Based on the answers, Zodb replaces the need for ORM. You can directly store the object inside the db(zodb itself).
It is said one of the zope's killer feature is the TTW(Through the Web or Developing using ZMI) philosophy. But I(and any developer) prefers File-System based development(using Version control, using Eclipse, using any favorite tool outside Zope). Then where is this TTW actually used?
This is the big one. What "EXTRA Stuff" does Zope's Acquistion gain when compared to Python/Django Inheritance.
Is it really a good move to come to Zope, from Django ?
Any site like djangosnippets.org for Zope(v2)?

First things first: current zope2 versions include all of zope3, too. And if you look at modern zope2 applications like Plone, you'll see that it uses a lot of "zope 3" (now called the "zope tool kit", ZTK) under the hood.
The real purpose of the ZODB: it is one of the few object databases (as opposed to relational SQL databases) that sees real widespread use. You can "just" store all your python objects in there without needing to use an object-relational mapper. No "select * from xyz" under the hood. And adding a new attribute on a zodb object "just" persists that change. Luxurious! Especially handy when your data cannot be handily mapped to a strict relational database. If you can map it easily: just use such a database, I've used sqlalchemy a few times in zope projects.
TTW: we've come back from that. At least, the zope2 way of TTW indeed has all the drawbacks that you fear. No version control, no outside tools, etc. Plone is experimenting (google for "dexterity") with nice explicit zope 3 ways of doing TTW development that can still be mapped back to the filesystem.
TTW: the zodb makes it easy and cheap to store all sorts of config settings in the database, so you can typically adjust a lot of things through the browser. This doesn't really count as typical TTW development, though.
Acquisition: handy trick, though it leads to a huge namespace polution. Double edged sword. To improve debuggability and maintenance we try to do without in most of the cases. The acquisition happens inside the "object graph", so think "folder structure inside the zope site". A call to "contact_form" three folders down can still find the "contact_form" on the root of the site if it isn't found somewhere in between. Double edged sword!
(And regular python object oriented inheritance happens all over the place of course).
Moving from django to zope: a really good idea for certain problems and nonsensical for other problems :-) Quite a lot of zope2/plone companies have actually done some django projects for specific projects, typically those that have 99% percent of their content in a relatively straightforward SQL database. If you're more into content management, zope (and plone) is probably better.
Additional tip: don't focus only on zope2. Zope3's "component architecture" has lots of functionality for creating bigger applications (also non-web). Look at grok (http://grok.zope.org) for a friendly packaged zope, for instance. The pure component architecture is also usable inside django projects.

On the ZODB:
Another way to ask "What is the real purpose of the ZODB?" is to ask, "Why was the ZODB originally created?"
The answer to that is the project was started very early on, around 1996. This was before the existance of MySQL or PostgreSQL, when miniSQL (a free-to-use but not free software) database was still in common use, or big money databases such as Oracle. Python provided the pickle module to serialize Python objects to disk - but serialization is lower level, it doesn't allow for features such as transactions, concurrent writes, and replication. This is what the ZODB provides.
It's still in use today in Zope because it works well. If you have no existing skillset in realational databases, it's easier to learn to use the ZODB than a relational database. It's also usable simpler use-cases, for example if you have a command-line script that needs to store some configuration information, using a relational database means having to run a database server just to store a little bit of configuraiton. You could use a config file, but the ZODB also works quite nicely because it's an embedable database. That means that the database is running in the same process as the rest of your Python code.
It's also worth noting that the API used to store objects inside containers is different between Zope 2 and Zope 3. In Zope 2, containers are stored as attributes:
root.mycontainer.myattr
In Zope 3, they use the same interface as Python standard dictionary type:
root['mycontainer']myattr
This is another reason why it can be easier to learn to use the ZODB than the Django ORM, since Django has it's own interface for it's ORM which is distinct from Python's existing interfaces.
Through-the-web (TTW):
Again, understanding the reason for TTW goes back when Zope was developed. While it seems silly to break with well known developer tools such Subversion or Mercurial, Zope was developed in the late 90s when the only free version control system was CVS. Zope 2 had it's own simple version control capabilites, and they were as good as CVS (which is to say, "they were limited and sucky."). UNIX workstations cost a lot more money back then, and had far fewer resources, so System Administrators were much more guarded and careful about how servers were managed. TTW allowed people who might not normally be able to upload code to the server with sysadmin intervation a way to do that.
With text editors, emacs and vi have had ftp-modes, and Zope 2 can listen on an FTP port. This would allow you to develop so that code was stored in the ZODB (editable TTW), but it was common to edit this code using a emacs or vi.
Today in Zope, TTW is more rarely used or promoted since it no longer makes sense to do this. Disk space is cheap, servers are (relatively) cheap, and there are lots of developer tools which expect to interact with the standard filesystem.
Acquisition:
It was a mistake. It was a very confusing feature that caused lots of unexpected things to happen. In theory there are some interesting ideas to acquisition, but in practice it's best tossed in the bin and has little practical use.
Moving from Django to Zope:
Work started on Zope 3 in 2001. This fixed a lot of the problems with Zope 2. It's a testament to the Zope community that Zope 2 is still actively and well maintained, but it's hardly state-of-the-art. Zope 2 is really only interesting to learn from a historical perspective.
Zope 3 ended up getting evolved in a few different directions, and so modern incarnations of Zope are best expressed in the form of Grok, BFG or Bobo.
Grok is closest to Zope 3, and as such is a pretty large framework - it can be rather overwhelming at times when delving through it's code base. However, just like Django, or any other full-stack framework you don't need to use every part of Grok, it can be quite easy to learn the basic and create web applications with it. It's convention-over-configuration is second to none, and it's class-based Views give it a much tighter, arguably cleaner code base than a Django web application. It's URL routing system is extremely flexible, but also arguably over-engineered.
BFG is a "pay for only what you eat" framework written by long time Zope developer Chris McDonough. As such, it's closer to Pylons in spirit, where only the parts deemed core or essential to a framework are included. It also plays very well with WSGI. It only uses a few core Zope packages.
Bobo is a "micro-framework". It's just a way to route URLs and serve up an app. It doesn't use any Zope packages, so isn't strictly in the Zope family of web frameworks. But it was written by Zope's creator, Jim Fulton, who originally called the publishing part of Zope, "Bobo". The original Bobo, written in the early 90's, mapped URLs to packages and modules, so if your source code was layed out as:
mypackage.mymodule.MyClass
You could have a URL such as:
/mypackage/mymodule/MyClass
Which was very inflexible, and was replaced with URL Traversel in Zope 2, which is fairly complex. Bobo uses Routes, so it's a middle ground between dead-simple URL resolution and complex URL resolution - about the same in complexity as Django's URL resolution machinery.

I answer without much experience on both, but I had the chance to manipulate both, so I can tell you my opinion on some of your questions.
1)What is the "real" purpose of zodb
as such? Meaning I know what it does,
but tell me one great thing that zodb
does and a framework like django(which
doesn't have zodb) misses
Load distribution via ZEO and search via ZCatalog. Django is very low level on this point of view. To achieve the same, you would have to reimplement a lot of wheels, triangular.
Something I learned quite soon is: don't mess with low level database issues. You will screw them up. It's a can of worms, Dune sized.
So why choose django ORM ? You should also consider if YAGNI. django is easy and self contained, documentation is premium, and when (if) your site will grow that much, you will do the switch to a better ORM (or to a pure OODB, in case of ZODB) later on.
2)It is said one of the zope's killer
feature is the TTW(Through the Web or
Developing using ZMI) philosophy. But
I(and any developer) prefers
File-System based development(using
Version control, using Eclipse, using
any favorite tool outside Zope). Then
where is this TTW actually used?
I cannot answer properly to this question, but I would not say that it's fundamentally bad to develop with such approach. Of course it's a change of mindset, and I tend to prefer filesystem based development as well.
4)Is it really a good move to work on
Zope, from Django ?
Zope 3 is very modular, so you are free to use many of its components from django. I would advise against it though. You can, of course, but what I found most problematic is the lack of help. There are not many people using zope components and django at the same time. Sooner or later, you will have a problem and google won't help. At that point, you will realize that if your life was a videogame, you are definitely playing it at level difficult (maybe extreme, if you will have to put your nose into the zope code).

A very good reference on ZODB is ZODB/ZEO programmer's guide. ZODB is not an ORM. Its a true object database. Python objects are persisted inside the database transparently without any worries about how to transform them into a representation suitable for database. Any pickleable Python object can be saved inside the ZODB. Relational databases are suitable for large amount of flat data (like employee records) while ZODB is best for hierarchical data (typically found in web applications). I personally use Zope 3 for my applications. I never did TTW type of work. Best part of using ZODB was the fact that I never had to worry at all about how I am going to save data and how things would change when I upgrade my software from one version to next one. For example, if I add a new attribute to a Python class, all I have to do is provide a default value as a class attribute. It then becomes automatically available to all objects created with the previous version of the same class. Removing an attribute is a simple del operation on existing objects. BTW, ZODB can be used independently in any kind of Python application and isn't coupled with just ZOPE platform. I love the fact that I don't have to worry about the nitty gritties of SQL while working on Python applications thanx to ZODB. And off course if you need a database server so that you can run multiple copies of your application backed by the same server ZEO comes to your rescue on top of ZODB.
Zope started with the idea of being an Object Publishing Environment. From that perspective mapping the URL directly to the object hierarchy in ZODB was great. The URLs simply reflect the hierarchy of objects. Now so far as figuring out the URL is considered, there is always the Rotterdam debugging interface for help. For development work, I keep the development flags on in the zope configuration and look at the contents of ZODB through the Rotterdam interface. Rotterdam skin provide a great way of introspecting the Python objects stored inside the ZODB and figuring out the URLs is much more interactive. Moreover, for major containers inside my ZODB, I register them as persistent utilities inside the site manager (Zope 3 sites and site managers). Anywhere in my code, whenever I need access to such containers, all I do is getUtility(IMyContainerType). I don't even have to remember the detailed locations of those containers inside the code base. They are once registered with the site manager and going forward available anywhere inside the code base through getUtility() calls.
And the URLs also support namespaces. For example using the ++skin++ namespace, you can anytime change the skin of your web application. Using the ++language++ namespace, you can any time change the preferred language of your user interface. Using the ++attributes++ namespace you can access individual attributes of an object. URLs are simply much more powerful and much more customizable. And you can write traversal adapters, define your own namespaces, to enhance the capabilities of your URLs. To give an example, all pages which are directly accessible from the web interface, are part of my default skin. While all pages which are invoked through background AJAX calls, are under a different skin. This way, one can implement different ways of authentication mechanisms in different skins. In main skin, one is redirected to a different login page in case of authentication failure. For AJAX pages, one could simply receive an HTTP error. This could be centrally done. Zope 3 objects have interfaces and one view can be defined for multiple interfaces. Wherever you have an object which supports the given interface, all associated views become automatically available and all such URLs are automatically valid. If you think about it, its a much more powerful than a single python file or XML file where the URLs are hard-coded. I don't really know much about DJango and J2EE so cannot say if they have equivalent capability.

ZODB is a OO-style database that doesn't need a schema definition. You can simply create (nearly) all kinds of objects, and persist them.
The TTW is sometimes annoying, but you can mount the ZOPE-object-tree using webdav. Then you can edit the templates and scripts using your favorite editor.
ZOPE is especially powerful for creating CMS-like systems, IMHO there it is still unmatched - you'd have to go through a lot to make it work equally well in Django.
And through the TTW, actually non-developers like designers have a good chance of developing e.g. templates and CSS without need for developer interaction.

+1 on Wheat's answer, above: "Zope 2 is really only interesting to learn from a historical perspective". I did Zope dev for a large site for a couple of years, 50% zope 2, 50% zope 3. Even then (this was 2 years ago) we were working to migrate everything off of zope 2. Unless you already have a lot invested in an existing Zope 2 project, there's no reason to use it; there's just not much of future there. And if you do have a big existing zope 2 project, I'd suggest taking a look at a product caled Five (a joke: 2 + 3 = 5) that aims to
allow you to integrate Zope 3
technologies into Zope 2. Among
others, it allows you to use Zope 3
interfaces, ZCML-based configuration,
adapters, browser pages (including
skins, layers, and resources),
automated add and edit forms based on
schemas, object events, as well as
Zope 3-style i18n message catalogs.
When all is said and done, Zope 3 is a very different framework from 2, and IMHO, a much better (albeit more complicated) one. TTW is optional, and not recommended for most cases. Implicit acquisition is gone.
Looks like people here have covered why you might want to use the ZODB, so I thought I'd mention one other thing about Zope 3 (or Zope 2 using Five) that's good. Zope has a very powerful system for wiring together different application components called the Zope Component Architecture (ZCA). It allows you to write components that are more or less autonomous and reusable, and which can be plugged together in a standardized way. I mostly do Django development now and I sometimes find myself missing the ZCA. In Django, the ability to write reusable components is limited and kind of ad-hoc. But, like Reinout says zope.component (like most zope packages, including the ZODB) works outside of the zope framework and could be used in a Django project.
That said, the ZCA has its drawbacks, one of which is the tedious process of registering your components in XML files; it always felt a little Java-esqe to me. One reason I really like Grok http://grok.zope.org/ is that it sits on top of zope.component and does much of that grunt work for you.
So bottom line: Zope 2 is mostly a dead end. If your employer is amenable to it, start looking at Zope 3, or at least Five. I think you'll find Zope 3 has a steep learning curve compared to Django, so it might be a good idea to come at it via Grok, which smooths out a lot of Zope 3's rougher edges. But, I think for a really large or complex web application with lots of moving parts, I'd go for Zope over Django (and I say this as someone who really likes Django a lot). For smaller projects, Django would probably be faster. Quantifying "large" and "small" in this context is hard though, and would probably require a couple of thousand more words. If you really are interested in Zope 3, the book by Philipp von Weitershausen is definitely the place to start.