[Python-3000] Method to populate tp_* slots via getattr()?

[Nick Coghlan]

One of the issues with porting to Py3k is the problem that __getattr__ 
and __getattribute__ can't reliably provide special methods like __add__ 
the way __getattr__ could with classic classes. (As first noted by Terry 
Reedy years ago, and recently seeing some new activity on the bug 
tracker [1])

The culprit here is the fact that __getattribute__ and its associated 
machinery is typically never invoked for the methods with dedicated tp_* 
slots in the C-level type structure.

What do people think of the idea of providing an extra method on type 
objects that goes through all of the C-level special method slots, and 
for each one that isn't currently set, does a getattr() on the 
associated special name and stores the result (if any) on the current 
type object?

When converting a proxy class that relies on __getattr__ from classic to 
new-style, all that would then be needed is to invoke the new method on 
the class object after defining the class (a class decorator or 
metaclass could be provided somewhere to make this a bit tidier).

This seems a lot cleaner than expecting everyone that implements a proxy 
object to maintain there own list of all of the relevant special 
methods, and locates the implementation support in an area of the code 
that already has plenty of infrastructure dedicated to keeping Python 
visible attributes in sync with the C visible tp_* slots.

Thoughts? Altenative ideas? Howls of protest?

Cheers,
Nick.

[1] http://bugs.python.org/issue643841

-- 
Nick Coghlan   |   ncoghlan at gmail.com   |   Brisbane, Australia
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