Introduction to Akhet 2ΒΆ

This chapter recounts Akhet’s history and current status. The next chapter introduces some vocabulary terms. The third chapter summarizes how to create a Pyramid application using the recommended skeleton, and how to use the Pyramid and Akhet development versions. The subsequent chapters analyze different aspects of the default application, and discuss various enhancements you can add to it. The final chapters discuss other Pyramid topics.

Akhet evolved out of a Pyramid/SQLAlchemy application scaffold. It then grew more Pylons-like features, a small library, and documentation that expanded to become a general introduction to Pyramid. In Akhet 2, the documentation takes center stage and the scaffold has been retired. Why this reversal? Mainly because it’s so much work to maintain a scaffold. (The scaffold rant appendix has the full details.) Also, Pyramid 1.3 consolidates the built-in scaffolds to three well-chosen ones.

Routing mechanism Database Pyramid 1.3 scaffold Pyramid 1.2.4 scaffold
URL dispatch SQLAlchemy alchemy routesalchemy
URL dispatch - starter -
Traversal ZODB zodb zodb
Traversal SQLAlchemy - alchemy
Traversal - - starter

The Pyramid 1.3 scaffolds emphasize on the two most widely-used application styles: URL dispatch with SQLAlchemy, and traversal with ZODB. The scaffold names are simplified to focus on this goal. The ‘starter’ scaffold switches to URL dispatch because it’s more appropriate for beginners. Using traversal at all is an advanced topic, and especially with SQLAlchemy. (If you want to see how traversal with SQLAlchemy can be implemented robustly, check out the Kotti content-management system.)

For those coming from Akhet 1, Pylons, Django, Rails, and similar frameworks with something akin to Routes, URL dispatch and SQL databases will be somewhat familiar. For those coming from a Java servlet or PHP-without-a-framework background, URL dispatch will be new but it’s a good rule-based way to handle URLs. Traversal is an entirely different concept, which is most useful when site users are allowed to create their own URLs with multiple levels (as in a content-management system or file manager). Traversal maps naturally to nested objects, which is why it’s often paired with an object database.

So this Akhet book and the Pyramid developers both recommend that new users start with the ‘alchemy’ or ‘starter’ scaffold in Pyramid 1.3, or the ‘routesalchemy’ scaffold in Pyramid 1.2. The rest of this book is based on those scaffolds.

Two other changes in Pyramid 1.3 deserve mention. One, it’s compatible with Python 3, and it drops Python 2.5 support. Akhet 2.0 does not do either of these yet, but the next version probably will.

Two, as part of the Python 3 porting, Pyramid 1.3 dropped its Paste and PasteScript dependencies. These will probably not be ported to 3 for reasons listed in the scaffold rant. This has the following consequences:

  • The ‘paster’ command is gone. It’s replaced by ‘pcreate’ and ‘pserve’.
  • The default HTTP server is now Wsgiref, the one in the Python standard library. You can use it during development and switch to a more robust server for production (PasteHTTPServer, CherryPy, mod_wsgi, FastCGI, etc).
  • PasteDeploy is <i>not</i> dropped, so the INI files still work the same way.

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