使用Python派生类在父类的方法？

Question

我可以迫使一个父类调用派生类的版本功能？

class Base(object):
    attr1 = ''
    attr2 = ''

    def virtual(self):
        pass               # doesn't do anything in the parent class

    def func(self):
        print "%s, %s" % (self.attr1, self.attr2)
        self.virtual()

和一个类，从中导出

class Derived(Base):
    attr1 = 'I am in class Derived'
    attr2 = 'blah blah'

    def virtual(self):
        # do stuff...
        # do stuff...

消解含糊：

d = Derived()
d.func()         # calls self.virtual() which is Base::virtual(), 
                 #  and I need it to be Derived::virtual()

Answer 1

如果您实例化一个Derived（比如d = Derived()），这是由.virtual名为为 d.func()的Derived.virtual。如果没有涉及Derived的实例，则有一个为self没有合适Derived.virtual等当然这是不可能的调用它。

Answer 2

这不是不可能的 - 有解决的办法其实，你不必在功能或类似的东西通过。我工作的一个项目，我自己在那里这个确切的问题上来。这里是解决方案：

class Base(): # no need to explicitly derive object for it to work
    attr1 = 'I am in class Base'
    attr2 = 'halb halb'

    def virtual(self):
        print "Base's Method"

    def func(self):
        print "%s, %s" % (self.attr1, self.attr2)
        self.virtual()

class Derived(Base):
    attr1 = 'I am in class Derived'
    attr2 = 'blah blah'

    def __init__(self):
  # only way I've found so far is to edit the dict like this
        Base.__dict__['_Base_virtual'] = self.virtual

    def virtual(self):
        print "Derived's Method"

if __name__ == '__main__':
    d = Derived()
    d.func()

Answer 3

好，我刚结束了传递的虚拟实例（）我需要FUNC（）

class Base(object):
    attr1 = ''
    attr2 = ''

    def __init__(self):
        pass

    def virtual(self):
        pass

    def func(self, cb):
         print "%s, %s" % (self.attr1, self.attr2)
         cb()

class Derived(Base):
    attr1 = 'I am in class Derived'
    attr2 = 'blah blah'

    def virtual(self):
        # do stuff...
        # do stuff...


d = Derived()
d.func(d.virtual)