horizon defaulst new

# a lot of code ommitted
class FilterAction(object):
    def __init__(self, **kwargs):
        # setting default attributes for base class (lets say this class is base)
        self._set_default(kwargs, 'important_attribute', "Important attribute")

    # this method will be defined in BaseAction so it will be in one place
    # it will be used for setting all default values, so it is consistent in all classes
    def _set_default(self, kwargs, key, default):
        value = (kwargs.get(key) if kwargs.get(key) is not None
                                 else default)
        setattr(self, key, value)

class MyGreatFilterAction(FilterAction):
    def __init__(self, **kwargs):
        super(MyGreatFilterAction, self).__init__(**kwargs)
        # redefining default attributes values for this class
        self._set_default(kwargs, 'important_attribute', "I am not so important in this class")


    def print_important_attribute(self):
        print self.important_attribute

m = MyGreatFilterAction(important_attributes=None)
m.print_important_attribute()

# the 'bla' attribute is just thrown away, beacause
# no level of inheritance tree assigns it as attribute of the object
# It could also throw exception when unknown attribute is given
m = MyGreatFilterAction(important_attribute="I can be important for this object", bla="blah")
m.print_important_attribute()