Method Resolution Order (MRO) in new-style classes?

Question

In the book Python in a Nutshell (2nd Edition) there is an example which uses
old style classes to demonstrate how methods are resolved in classic resolution or

Answer 1

The result you get is correct. Try changing base class of Base3 to Base1 and compare with the same hierarchy for classic classes:

class Base1(object):
    def amethod(self): print "Base1"

class Base2(Base1):
    pass

class Base3(Base1):
    def amethod(self): print "Base3"

class Derived(Base2,Base3):
    pass

instance = Derived()
instance.amethod()


class Base1:
    def amethod(self): print "Base1"

class Base2(Base1):
    pass

class Base3(Base1):
    def amethod(self): print "Base3"

class Derived(Base2,Base3):
    pass

instance = Derived()
instance.amethod()

Now it outputs:

Base3
Base1

Read this explanation for more information.