Examples of descriptors?

[Mike C. Fletcher]

Definition:

    An object which mediates access to a class instance's attributes via
    a specific API.

Examples:

Built-ins property, classmethod, staticmethod.

OpenGLContext's fields -- implement VRML97 field semantics for 
scenegraph nodes, with coercian, type-checking, and observability.  
Focus on providing consistent, fast representations of field values for 
the run-time engine.  Implemented as sub-classes of properties at the 
moment, though likely to switch to raw descriptor API soon.  Includes a 
C accelerator module to speed up the __get__ method.

http://cvs.sourceforge.net/cgi-bin/viewcvs.cgi/pyopengl/vrml/field.py?rev=HEAD&content-type=text/vnd.viewcvs-markup
http://cvs.sourceforge.net/cgi-bin/viewcvs.cgi/pyopengl/vrml/fieldtypes.py?rev=HEAD&content-type=text/vnd.viewcvs-markup

wxPython Properties Distribution properties -- generic typed properties, 
coercian, type-checking, emphasis on ability to extend the set of 
property types readily, (e.g. with unions of types, lists-of-types, 
etceteras), focuses mostly on "business" objects and supporting GUI 
editing of those objects' properties.  Implemented using the raw 
descriptor API.

http://cvs.sourceforge.net/cgi-bin/viewcvs.cgi/wxpypropdist/properties/basicproperty/basic.py?rev=HEAD&content-type=text/vnd.viewcvs-markup
http://cvs.sourceforge.net/cgi-bin/viewcvs.cgi/wxpypropdist/properties/basicproperty/common.py?rev=HEAD&content-type=text/vnd.viewcvs-markup

Enjoy,
Mike

Edward C. Jones wrote:

> What, exactly, is a "descriptor"? The closest thing to a definition 
> that I can find is: a class that defines __get__, __set__, and 
> __delete__. Where can I find some examples?
>
> Ed Jones

_______________________________________
  Mike C. Fletcher
  Designer, VR Plumber, Coder
  http://members.rogers.com/mcfletch/