class A:
def f(self):
print('A.f')
class B(A):
pass
class C:
def f(self):
print('C.f')
class D(B, C):
pass
D().f() # => A.f
class A:
def f(self):
print('A.f')
class B(A):
pass
class C:
def f(self):
print('C.f')
class D(B, C):
pass
D().f() # => A.f