Diamond Pattern in Python 3

diamond_awesomepattern.py

print(r'''
    The Classic Diamond Pattern
          or
    How I Learned to Stop Worrying and Love Python


    --> := 'inherets from'

        A
        ^
       / \
      /   \
     B <-- C
     ^     ^
      \   /
       \ /
        D
''')

class A(object):
    def __init__(self,a):
        print('  A.init')
        self.a = a
    def fn(self):
        print('    A.fn',self.a)

class B(A):
    def __init__(self,a,b):
        print('  B.init')
        super().__init__(a)
        self.b = b
    def fn(self):
        print('    B.fn',self.a,self.b)
        super().fn()

class C(B,A):
    def __init__(self,a,b,c):
        print('  C.init')
        super().__init__(a,b)
        self.c = c
    def fn(self):
        print('    C.fn',self.a,self.b,self.c)
        super().fn()

class D(C,B):
    def __init__(self,a,b,c,d):
        print('  D.init')
        super().__init__(a,b,c)
        self.d = d
    def fn(self):
        print('    D.fn',self.a,self.b,self.c,self.d)
        super().fn()

print('A(1)')
a = A(1)
print('B(1,2)')
b = B(1,2)
print('C(1,2,3)')
c = C(1,2,3)
print('D(1,2,3,4)')
d = D(1,2,3,4)

print('a.fn()')
a.fn()
print('b.fn()')
b.fn()
print('c.fn()')
c.fn()
print('d.fn()')
d.fn()