[Python-Dev] Backport PEP 3129: Class Decorators (original) (raw)

Eli Courtwright eli at courtwright.org
Tue Jan 8 17:42:07 CET 2008

Since we're talking about class decorators, I have a question about function and instancemethod objects. The following code works

class Root(object): def index(self): return "Hello World!" index.exposed = True

but this code

class Root(object): def index(self): return "Hello World!" index.exposed = True

gives the following exception

Traceback (most recent call last): File "", line 1, in AttributeError: 'instancemethod' object has no attribute 'exposed'

I can tell that instancemethods can't have attributes added to them outside of their class definition. Is this part of the Python language spec, or just an implementation detail of CPython?

I bring this up here because it makes writing certain class decorators much more annoying. For example, if I want to write a class decorator that will set "exposed=True" for every method of a class, I must resort to shenanigans.

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