python - 通过 Mixin 调用 Grandparent Method 而不执行父方法

Question

我需要覆盖Parent 方法并通过mixin 调用Grandparent 方法。是否可以？

例如:A 和B 是库类。

class A(object):
    def class_name(self):
        print "A"


class B(A):
    def class_name(self):
        print "B"
        super(B, self).class_name()
    # other methods ...

现在我需要重写 B 的 class_name 方法并将其称为 super。

class Mixin(object):
    def class_name(self):
        print "Mixin"
        # need to call Grandparent class_name instead of parent's
        # super(Mixin, self).class_name()


class D(Mixin, B):
    # Here I need to override class_name method from B and call B's super i.e. A's class_name, 
    # It is better if I can able to do this thourgh Mixin class. (
    pass

现在当我调用 D().class_name() 时，它应该只打印 "Mixin"和 "A"。不是“B”

Answer 1

一种方法是使用 inspect.getmro()但如果用户编写 class D(B, Mixin)，这可能会中断。

让我演示一下:

class A(object):
    def class_name(self):
        print "A"


class B(A):
    def class_name(self):
        print "B"
        super(B, self).class_name()
    # other methods ...

class Mixin(object):
    def class_name(self):
        print "Mixin"
        # need to call Grandparent class_name instead of parent's
        # super(Mixin, self).class_name()


class D(Mixin, B):
    # Here I need to override class_name method from B and call B's super i.e. A's class_name, 
    # It is better if I can able to do this thourgh Mixin class. (
    pass

class E(B, Mixin): pass

import inspect
print inspect.getmro(D) # returns tuple with (D, Mixin, B, A, object)
print inspect.getmro(E) # returns tuple with (E, B, A, Mixin, object)

所以如果你有控制权并且可以确保你总是首先得到Mixin。您可以使用 getmro() 获取祖 parent 并执行它的 class_name 函数。