Thanks, everyone, for your replies. Perhaps I have complicated things unnecessarily? I was just trying to do some error-checking on the arguments supplied to the class constructor. Perhaps Python already implements automatically what I am trying to accomplish manually? I'll tinker around with some minimal code, try to provoke some errors, and see what I get.
Here is one more detail which may be relevant. The base class for the family of classes I am developing is a numpy.ndarray. The numpy.ndarray is a C extension type (and if I understand correctly, that means it is immutable by ordinary Python methods). Subclassing ndarray can get a bit complicated (see http://docs.scipy.org/doc/numpy/user/basics.subclassing.html). The ndarray.__init__ method is inaccessible, instead one overrides ndarray.__new__. Making further subclasses of a subclassed numpy.ndarray, each of which may have their own arguments, is what I am trying to accomplish while adhering to the "DRY" principle. -- https://mail.python.org/mailman/listinfo/python-list
