On 8 May 2016 at 08:39, Serhiy Storchaka <storch...@gmail.com> wrote: > Should alternative constructor call __new__ and __init__ methods? Thay can > change signature in derived class.
I think this is typically the way to go (although, depending on the specific type, the unpickling related methods may be a more appropriate way for the alternate constructor to populate the instance state) > Should it complain if __new__ or __init__ were overridden? If there are alternate constructors that depend on either the signature of __new__/__init__, unpickling support, or some other mechanism for creating new instances, this should be mentioned in the class documentation as a constraint on subclasses - if subclasses don't want to meet the constraint, they'll need to override the affected alternate constructors. Cheers, Nick. P.S. The potential complexity of that is one of the reasons the design philosophy of "prefer composition to inheritance" has emerged - subclassing is a powerful tool, but it does mean you often end up needing to care about more interactions between the subclass and the base class than you really wanted to. -- Nick Coghlan | ncogh...@gmail.com | Brisbane, Australia _______________________________________________ Python-Dev mailing list Python-Dev@python.org https://mail.python.org/mailman/listinfo/python-dev Unsubscribe: https://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
