Greatest Common Superclass

Question

Is there any simple way to get the "greatest common superclass" of a list of objects? For example, if

class A(object): pass
class B(A): pass
class C(A): pass
class D(B, C): pass
class E(C): pass
class F(D, E): pass

and

b = B()
d = D()
e = E()

then

gcs(b, e) is A
gcs(d, e) is C
gcs(e, e) is E

Answer 1

Based on Martijn's idea, but using an easier approach considering that time complexity is not going to be an issue here(Thanks to @veedrac for his inputs):

def gcs(*instances):
    classes = [type(x).mro() for x in instances]
    for x in classes[0]:
        if all(x in mro for mro in classes):
            return x

print gcs(b, e)
print gcs(d, e)
print gcs(e, e)

Output:

<class '__main__.A'>
<class '__main__.C'>
<class '__main__.E'>

A slight variant of the above code using sets:

def gcs(*instances):
    mros = (type(ins).mro() for ins in instances)
    mro = next(mros)
    common = set(mro).intersection(*mros)
    return next((x for x in mro if x in common), None)