Can a Zope-internals guru provide some enlightenment regarding the mysteries of __init__? I'm writing some zproducts that subclass the existing Folder class, and then are themselves subclassed. What I've got works, but I'm not sure its _correct_. As I'm writing a "Zope Best Practices" document, I'd like to get it right. As I understand it, the use of __init__ should be avoided when possible, since it isn't invoked (necessarily) when persistent objects are reloaded from disk. Therefore Zope tends to do instance init within manage_addMYPRODUCT global-to-Zope functions, although this doesn't seem to be fully consistent throughout the Zope community contributions. The scenario is something like the following: def manage_addFolder(self, id, title='', ...): instance = Folder() instance.id = str(id) instance.title = title self._setObject(id, instance) class Folder(...): # no __init__ method def manage_addLargeFolder(self, id, title='', ...): instance = LargeFolder() instance.id = str(id) instance.title = title self._setObject(id, instance) class LargeFolder(Folder): def __init__(self): # parent class has no __init__ so don't call it! #Folder.__init__() self._tree = OOBTree() def manage_addSpecialLargeFolder(self, id, title='', ...): instance = SpecialLargeFolder() instance.id = str(id) instance.title = title self._setObject(id, instance) class SpecialLargeFolder(LargeFolder): def __init__(self): # parent class DOES have an __init__ so call it LargeFolder.__init__() self._other = OOBTree() (A) I reluctantly found it necessary to add an __init__ to my LargeFolder class because if I init'd self._tree in manage_addLargeFolder(), then it won't get init'd when manage_addSpecialLargeFolder() is used to create instances. manage_addLargeFolder doesn't get invoked in that case. (B) Currently the Folder class lacks an __init__ so I cannot call it from LargeFolder.__init__, but if someday ZC decides to add one, my code will fail to init Folder and break. Is this correct? I wish Python auto-provided a default no-nothing __init__ for this case so I could always call it. So the Guiding Rule seems to be "initialize those attributes that are common to all Zope objects, e.g. id and title, within the factory functions, but init any attributes you introduce using an __init__ method." Correct? -Jeff Rush