[Python-3000] Generic functions vs. OO

[Phillip J. Eby]

At 02:34 PM 11/27/2006 -0500, Jim Jewett wrote:
>I'm not sure that adding it to the builtin (but in a new name) would
>really buy much over an adapter (x in MyProto("asdf") ), but the
>interface fans may feel differently.

For what it's worth, in Chandler there is a system called Annotations that 
allows third-party packages to add private attributes to existing 
(persistent) data types.  It's used to implement "stamping", which is a way 
that you can (for example) dynamically change a note or photo into a task 
or a calendar event.

So, if I want to be able to add calendar information to "stampable" 
objects, I can do something like:

     class CalendarEvent(Stamp):
         # field definitions here
         # method definitions

And then I can access fields on stamped items by using e.g. 
CalendarEvent(someItem).startTime.  So, effectively CalendarEvent is a kind 
of adapter class, but we don't use the word adapter, simply because it 
isn't relevant to the application domain.  It's simply a way of having an 
open system for adding additional data to existing object types.  There are 
no interfaces or generic functions involved, either, it's just a way of 
separating namespaces belonging to independent developers.

I just mention it because the reaction to it among developers with no 
previous exposure to Python adaptation has been fairly positive.