jeremito wrote: > I am writing a class that is intended to be subclassed. What is the > proper way to indicate that a sub class must override a method?
You can't (easily). If your subclass doesn't override a method, then you'll get a big fat AttributeError when someone tries to call it. But this doesn't stop someone from defining a subclass that fails to override the method. Only when it's called will the error show up. You can, as others have noted, define a method that raises NotImplementedError. But this still doesn't stop someone from defining a subclass that fails to override the method. The error still only occurs when the method is called. There are some advantages to using NotImplementedError: 1. It documents the fact that a method needs to be overridden 2. It lets tools such as pylint know that this is an abstract method 3. It results in a more informative error message But, in the end, if someone wants to define a class that defiantly refuses to declare a method, you can't stop them. Carl Banks -- http://mail.python.org/mailman/listinfo/python-list
