python中的虛函數

class Super:
    def method(self):
        print 'in Super.method'

    def delegate(self):
        self.action()

class Inheritor(Super):

    pass
class Replacer(Super):

    def method(self):
        print 'in Replacer.method'
class Extender(Super):

    def method(self):
        print 'starting Extender.method'
        Super.method(self)
        print 'ending Extender.method'
class Provider(Super):

    def action(self):
        print 'in Provider.action'
if name == 'main':
    for klass in (Inheritor, Replacer, Extender):
        print '\n' + klass.name + '...'
        klass().method()

print '\nProvider...'
x = Provider()
x.delegate()</pre>