Get properties... on classes!

class_property.py

'''
Written January 4, 2012 by Josiah Carlson
Released into the public domain.

I've only ever needed this once, but I had to learn the descriptor protocol.
Works just like a property, except that what you decorate gets the class
instead of the instance.

class Example(object):
    @ClassProperty
    def foo(cls):
        return cls._foo

    @foo.setter
    def foo(cls, value):
        cls._foo = value

    @foo.deleter
    def foo(cls):
        del cls._foo

'''

class ClassProperty(object):
    def __init__(self, get, set=None, delete=None):
        self.get = get
        self.set = set
        self.delete = delete

    def __get__(self, obj, cls=None):
        if cls is None:
            cls = type(obj)
        return self.get(cls)

    def __set__(self, obj, value):
        cls = type(obj)
        self.set(cls, value)

    def __delete__(self, obj):
        cls = type(obj)
        self.delete(cls)

    def getter(self, get):
        return ClassProperty(get, self.set, self.delete)

    def setter(self, set):
        return ClassProperty(self.get, set, self.delete)

    def deleter(self, delete):
        return ClassProperty(self.get, self.set, delete)