Thank you both for your responses. I do have one other question if I use the method both of you describe. How do I go about implementing slicing and indexing for an object in python? A list object innately has them and that is really why I wanted to use it. I would appreciate it if you can point me to something.
Denis On Mon, Oct 11, 2010 at 4:13 AM, Alan Gauld <alan.ga...@btinternet.com>wrote: > > "Denis Gomes" <denisg...@gmail.com> wrote > > > I have a basic python question. I am writing an n dimensional vector >> class by inheriting from the builtin python list object. I want to be >> able to hide the parent object's methods in the derived class instances. >> > > Doing so would break the Liskofff Substitution Principle which says > you should be able to use your subclass anywhere that the parent > class can be used. This is a very bad thing! > > If you want to expose a reduced set of operations, rather than an > extended set, then inheritance is the wriong solution. You should > consider using delegation instead. Create a list indside your class > and forward any requests for the operations you do want to the > list object. > > The only snag with delegation in this scenartio is that you have > to write an awful lot of one-liner methods. To get round that > you can use setattr() and getattr() combined with a list of allowed > operation names. Check the operation is in the list and then > forward the request by name. That can save a lot of coding! > > HTH, > > > -- > Alan Gauld > Author of the Learn to Program web site > http://www.alan-g.me.uk/ > > > > _______________________________________________ > Tutor maillist - Tutor@python.org > To unsubscribe or change subscription options: > http://mail.python.org/mailman/listinfo/tutor >
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