Having defined a class using python like this one: from OFS import ObjectManager, SimpleItem class Plant(ObjectManager.ObjectManager, SimpleItem.SimpleItem): """A plant""" def __init__(self, name, responsible): "Inits the product with default values" self.name = name self.responsible = responsible self.areas = {} you create a few instances, and later you want to add more properties to the same class, for example: def __init__(self, name, responsible, address): "Inits the product with default values" self.name = name self.responsible = responsible self.areas = {} self.address = address Is there a way to programatically modify the existing instances and add this new property to them. Any help will be appreciated. Luis