On Sat, Mar 2, 2013 at 10:02 AM, gialloporpora <gialloporp...@gmail.com> wrote: > Hi all, > I would like to inherit from the list native class. > really I expected that was possible to use native list method without > redefining them, for example the __repr__ method. > > I don't know if i have made something wrong, this is my code (I obmit > customized methods that I have added): > > from os.path import exists > > class vector(list): > def __init__(self, *args): > self._list = list(args)
So here you have a list subclass, but instead of taking advantage of that is-a relationship, you're creating a secondary list from the arguments and attaching it to self._list in a has-a relationship. The net effect is that you actually have two separate list objects here, with some methods operating on the list itself and some operating on the attached list. Try this instead: class Vector(list): def __new__(cls, *args): return super(Vector, cls).__new__(cls, args) def __init__(self, *args): super(Vector, self).__init__(args) The __new__ method here will receive the args in the style that you want, and then pass them up the inheritance chain to the superclass constructor, which will then just do the right thing. The __init__ method is also overridden to match the modified argspec. The super().__init__() call is included for completeness; AFAIK it doesn't actually do anything. -- http://mail.python.org/mailman/listinfo/python-list