PythonScripts Vision

Problem

As Zope developers build increasingly complex applications, they find that DTML is a poor way to implement non-trivial application logic. DTML was never really intended for complex logic, but lack of an alternate way to express through-the-web editable logic has caused the "source" of many sites to become ugly and difficult to maintain as site developers push the envelope of DTML.

Of course, these developers could write ExternalMethods^x or PythonProducts^x instead, but for various reasons they often opt for the through-the-web convenience of DTML (even at the expense of clarity). Applications could become much more maintainable (and the outer limits of DTML pushed less) if significant logic were moved out of DTML and pushed into something more suited to logic.

Proposed Solution

The PythonScripts Product provides objects that can encapsulate more complex logic expressed in Python while retaining the through-the-web benefits that people like about DTMLMethods^x. There is already a prototype implementation of PythonScripts (PythonMethodsProduct^x) in fairly wide use. We propose to resolve the outstanding issues and make Python Scripts available as a standard object type in the Zope platform.

Core Python Script support will give developers "out of the box" the ability to better manage the complexity of their applications by putting significant logic into Python Scripts and leaving presentation issues to DTML. Python Script objects:

• Will allow logic to be written in a language suitable for logic (Python)

• Will be editable via the Web. FTP and DAV support are outside the immediate scope of the project (but may be added later after the initial release).

• Will be tightly integrated with the Zope security machinery. Because they will be editable via the web, they will enforce security restrictions very similar to those enforced in DTML. They will not allow access to arbitrary modules or potentially dangerous system or runtime resources.

• Can be used as ZClass^x methods as well as stand-alone objects.

• Will implement the MethodObjectInterface, which is an interface that has been in development to make it easier to work with method-like objects in a standard way and provides support for common problems specific to methods (such as control of binding).

• Will provide synchronized distribution of logic for free when used with ZEO.

Risk Factors

Please see the RiskFactors document.

Scope

This project will provide an implementation of Python Script objects to be included in the Zope core and associated documentation.

Deliverables

This project is expected to produce:

• A stable implementation of Python Script objects to be included in a future release of Zope

• Zope help system pages for each screen in the user interfaces of the objects in the product

• API documentation for inclusion in the help system covering the public interfaces of Python Script objects

• Documentation suitable for inclusion as a section of the Zope Content Manager's Guide covering the use of Python Scripts. This should include a detailed explanation of the "rules" that govern what you can and cannot do in Python Scripts.