Python在父类中使用派生类的方法？

Question

我可以强制父类调用派生类的函数版本吗？

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()

以及从中衍生出来的一类

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

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

清除模糊:

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

Answer 1

如果你实例化一个Derived(比如说d = Derived()),.virtual那个被调用的d.func() 是 Derived.virtual.如果没有Derived涉及的实例,则没有适合self的Derived.virtual,所以当然不可能称之为.

Answer 2

这并非不可能-实际上有一种解决方法，您不必传递函数或类似的东西。我自己正在一个项目中解决这个确切的问题。解决方法如下：

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()