How to set and get a parent class attribute from an inherited class in Python?

Question

I have the Family and its inherited Person classes. How do I get the familyName attribute from the Person class?

Answer 1

You cannot.

Instances only inherit the parent class methods and attributes, not instance attributes. You should not confuse the two.

strauss.familyName is an instance attribute of a Family instance. The Person instances would have their own copies of the familyName attribute.

You normally would code the Person constructor to take two arguments:

class Person(Family):
    def __init__(self, personName, familyName):
        super(Person, self).__init__(familyName)
        self.personName = personName

johaness = Person('Johaness', 'Strauss')
richard = Person('Richard', 'Strauss')

An alternative approach would be for Person to hold a reference to a Family instance:

class Person(object):
    def __init__(self, personName, family):
        self.personName = personName
        self.family = family

where Person no longer inherits from Family. Use it like:

strauss = Family('Strauss')
johaness = Person('Johaness', strauss)
richard = Person('Richard', strauss)

print johaness.family.familyName