Any difference in adding grandparent into MRO in python?

Question

Are there any side-effects of adding grandparent to the MRO? Purpose is I would like to get grandchildren classes by using grandparent.__subclasses__()

class A(object):
    def work(self):
        print 'A'


class B(A):
    def work(self):
        print 'B'
        super(B, self).work()


class C(B):
    def work(self):
        print 'C'
        super(C, self).work()

class D(B, A):
    def work(self):
        print 'D'
        super(D, self).work()

>>> C().work()
C
B
A
>>> D().work()
D
B
A
>>> A.__subclasses__()
[<class 'test.B'>, <class 'test.D'>]

What do you mean with side effects? You could determine the grandchildren by inspecting the MRO of each entry in `A.__subclasses__()`. — Simeon Visser, Jun 09 '15 at 21:48
@SimeonVisser how do you inspect each of grandchildren if you don't know `C` exists. `A.__subclasses__()` only returns immediate children. — James Lin, Jun 09 '15 at 21:53
Breadth-first search. Keep calling `__subclasses__` on subclasses until you hit bottom. — user2357112, Jun 09 '15 at 21:58
Yes, repeat the process one more step to obtain all children of all children. — Simeon Visser, Jun 09 '15 at 22:00

score 0 · Answer 1 · answered Jun 09 '15 at 22:24

We have come up a recursive function to work out the subclasses

def get_all_subclasses(cls):
    all_subclasses = []

    for subclass in cls.__subclasses__():
        all_subclasses.append(subclass)
        all_subclasses.extend(get_all_subclasses(subclass))

    return all_subclasses

Any difference in adding grandparent into MRO in python?

1 Answers1