class A:
   def func(self):
      print('A')
class B(A):
   # pass
   def func(self):
      print('B')
class C(A):
   def func(self):
      print('C')
class D(C):
   def func(self):
      print('D')

class E(B):pass
   # def func(self):
   #  print('E')
class F(E,D):pass
   #def func(self):
   #  print('F')

f=F()
f.func()

继承顺序遵循广度优先的原则