Question

class A (object):
    keywords = ('one', 'two', 'three')

class B (A):
    keywords = A.keywords + ('four', 'five', 'six')

Is there any way to change A.keywords to <thing B derives from>.keywords, sort of like super(), but pre-__init__/self? I don’t like repeating class names in definitions.

Usage:

>>> A.keywords
('one', 'two', 'three')
>>> B.keywords
('one', 'two', 'three', 'four', 'five', 'six')

Answer 1

Actually, you can. Write a descriptor that checks the class’s bases for an attribute with the same name and add the passed attributes to its value.

class parentplus(object):
    def __init__(self, name, current):
        self.name = name
        self.value = current

    def __get__(self, instance, owner):
        # Find the attribute in self.name in instance's bases
        # Implementation left as an exercise for the reader

class A(object):
    keywords = ('one', 'two', 'three')

class B(A):
    keywords = parentplus('keywords', ('four', 'five', 'six'))