To understand Plone's packaging story you must first understand both the historic Zope2 add-on packaging story and the present day Python packaging story. It also doesn't hurt to understand the future of Python packaging.
Zope2 introduces the concept of "products" which are bundles of Python source code that live in a special "products" directory; Zope2 looks for these on startup and then registers them if they meet a certain set of criteria.
The specialized creation and use of products in Zope2 has generally fallen out of favor, and given way to the use of generic Python packages, which are widely used by the rest of the Python community.
The Setuptools add-on module for Python introduces the concept of Python packages, called "eggs" (although recently, they are more and more being referred to as just packages to avoid any "cuteness" getting in the way of the concept.)
If the packaging story were over now, things would be simple; but life is never simple. What follows is an explanation of Setuptools vs. Distribute. Or if you will, old style (Setuptools) vs. new style (Distribute) within the new style of packaging (eggs).
Old style within new style
There are several important things you should know about Setuptools:
- It's built on top of a core module called Distutils, but it itself is not part of the Python core.
- It was forked in 2009 into the Distribute project (based on a disagreement over frequency of releases, among other things).
- It continues to exist.
Based on the above criteria, and what follows below about Distribute, you may sometimes (perhaps less frequently then in the case of products vs. packages) hear Setuptools referred to as "old style" and Distribute referred to as "new style". And even if you don't, being aware of the distinction will certainly help you understand "new style" packaging better.
New style within new style
Distribute is a fork of Setuptools. It is intended to "get us through" to the point where a better solution can be implemented within the Python core in the Distutils2 module which is currently in development (as of early 2011).
Distribute is actively maintained, has frequent bug fixes and releases, and is the self-proclaimed "new hotness".
And the "new hotness" part is no false promise. Using Distribute means you are using the newest Python packaging technology short of Distutils2. One of the promises of Distribute is using it will prepare you as gently as possible for the arrival of Distutils2.