On Thu, Feb 18, 2016 at 10:41 AM, Herman <sorsor...@gmail.com> wrote: > From: Ben Finney <ben+pyt...@benfinney.id.au> >> >> you are using the inheritance hierarchy but thwarting it by not using >> ‘super’. Instead:: >> >> super().__init__(self, default_factory, *a, **kw) >> >> and:: >> >> super().__getitem__(self, key) >> -- >> \ "Those who will not reason, are bigots, those who cannot, are | >> `\ fools, and those who dare not, are slaves." —“Lord” George | >> _o__) Gordon Noel Byron | >> Ben Finney > > super does not work for defaultdict. I am using python 2.7. If I use > super(defaultdict, self).__init__(default_factory, *a, **kw), I get the > error: > > super(defaultdict, self).__init__(default_factory, *a, **kw) > TypeError: 'function' object is not iterable
You're using it incorrectly. If your class is named DefaultDictWithEnhancedFactory, then the super call would be: super(DefaultDictWithEnhancedFactory, self).__init__(default_factory, *a, **kw) You pass in the current class so that super can look up the next class. If you pass defaultdict instead, super will think that it's being called *by* defaultdict and call the __init__ method on its own superclass, dict, which has a different signature. defaultdict.__init__ is effectively skipped. > Look like inheriting from defaultdict is easier. I don't even have to > override the constructor as suggested by Chris Angelico above. Thanks. True, although there's a faint code smell as this technically violates the Liskov Substitution Principle; the default_factory attribute on defaultdict instances is expected to be a function of zero arguments, not one. -- https://mail.python.org/mailman/listinfo/python-list
