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I've been trying to add some extra functionallity to a Folder object without inheriting, but I'm not able to make it work.

First question is "Why?". Unless you want to change the fucntionality of *all* folder objects inheriting is the way to go.

For instance, If I've a repository of Folders and Files and I write two applications using it. In the first application I need an extra method to obtain contained objects in some especific order, and in the second application I need a different order. I can write a new class inheriting from Folder with two diferent new methods, but I think that this is not a good aproach. If tomorrow I write a new application with some other needings I should modify my InheritedFolderClass. I prefer to add this logic in each application, using and adapter. If all we create inherited versions of Folders, collaborations between applications is more difficult. I you have an application using a repository of inheritedFolderA's and I have another one using inheritedFolderB's, our applications can't use the same repository, what would be possible using a repository of Folders and adapters in each application.

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Anybody knows if there is a way to use adapters in zope2 ? Or, if not, there is some other way to add functionallity on-the-fly, without inheriting ?

MonkeyPatching. Python is highly dynamic. You rewrite the methods to how you would like them, and then you replace them with a quick.

TheClass.OldMethod = NewMethod.

And now you call the new method with object = TheClass() object.OldMethod() Very cool.

Yes, this is a possible way, but not so nice as Adapters (in my modest opinion). Thanks for your answer Santi Camps http://zetadb.sourceforge.net