I am currently working in C# after I spent about 3 years almost only in python, The way I see thinks is that for me we need interfaces in C# to allow for flexibility in using OOP because we must only pass defined and known types at all times so for us to have the flexibility of passing either a Car or a Bus to the Mechanic when we actually only need their fixIt method we need to use a common type that will accommodate the constraint of having the fixIt method. Of course this could also be implemented using an abstract base class but since in C# as well as in Java we don't have multiple inheritance it is better to use an interface for flexibility purpose (for ex. sometime you have to subclass from MarshalByRefObject in order to use the object in a distributed system so inheritance is out of the question as a means to flexibility in that case).
So for good and flexible OOP in C# someone should use interfaces because it is the only way to achive the flexibility needed but in python because of duck typing you always get the flexibility without you doing anything special like trying to come up with a type that accommodates some common ground of other types, so as someone say here "To use interfaces in python, just do what you would do in Java, except don't use interfaces." So to digress a little, for me the difference is that in C# you are given safety, documentation (read app. domain definitions) and track-ability (read refactoring, intelisense) but you have to code for flexibility while in python you are given flexibility but you have to code for safety and documentation and as far as for track-ability you are usually out of luck. Now many people agree that the safety you are given in C# is usually far from ideal (no app. domain logic safety given) so usually you have to code for that as well as in python, and my opinion is that the documentation provided by type definition wile ok, for best maintainability you have to provide comments anyway about their app. domain means just like you do in python, so the only think that is different is that the lack of track-ability in python is sometime annoying for me now when I'm going back to python after a little bit of C#, but the annoyance is even bigger when in C# I always have to think ahead of time how to make sure that my code if flexible enough to support easy changing. Gheorghe Milas -- http://mail.python.org/mailman/listinfo/python-list
