This is probably obvious for the people that uses Repoze or Pylons, or early adopters in the Plone world, but from a Plone or a Zope developer perspective, you could live without it until now.

Now WSGI is everywhere.

I remember when Martijn Faassen brought the idea in 2006, of hooking Grok and Zope 3 into the WSGI. Maybe someone else talked about it before but that was the first time I could picture what WSGI could bring.

Now with the work done by people like:

The repoze team, that made it easier to run a Plone-based application in WSGI

The Paste Script / Paste Deploy team, that provided a simple way to describe a WSGI chain

And major WSGI middlewares like :

repoze.who which allows you to deal with authentication separately

Deliverance, which let you theme any application and let this application focus on delivering a content

Things like Beaker, which let you use memcached for instance, to store session data and cache arbitrary things

From a CTO point of view, a WSGI environment brings me the ability to think about a web application and build it without having to stick into one framework and try to bend all technologies inside it.

For instance:

I can write a Plone application and use Beaker to deal with sessions, without having to wrap Memcached into a custom plone package.

I can ask a graphic designer to work on a CSS and a layout without having to do it into Plone. It’s not that Plone design tools are bad, but the learning curve of writing a rule file in Deliverance and apply it to any piece of application makes the designer more productive than becoming a specialist of one skinning tool.

If my customer use moinmoin as a Wiki, I can put it into my Plone site transparently by defining a composite section in my Paste configuraton file.

…

You could do all the mentioned thing without WSGI, just by importing the packages and/or dealing with proxies at Apache level. But that is not the point.

The point is that WSGI brought the idea of making all web frameworks and libraries interact together to build one web application.

It is not the silver bullet of course, but my gut feeling is that this will create some kind of reunification in Python Web development communities: people are starting to look at a wider range of package, beyond the framework they use everyday.