On Jan 4, 2007, at 9:28 PM, Carl Banks wrote: > 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.
This is the con of a dynamic language... -- http://mail.python.org/mailman/listinfo/python-list
