无法创建一致的方法解决方案。为什么？ [关闭]

Question

我在多重继承中遇到错误。由于我是 python 新手，所以我不明白为什么我不能这样做。

class A(object):
    def say_hello(self):
        print 'A says hello'


class B(A):
    def say_hello(self):
        super(B, self).say_hello()
        print 'B says hello'

class C(A):
    def say_hello(self):
        super(C, self).say_hello()
        print 'C says hello'

class D(A, B):
    def say_hello(self):
        super(D, self).say_hello()
        print 'D says hello'

DD = D()
DD.say_hello() 

我收到错误：- 无法创建一致的方法解决方案。为什么？

Answer 1

D 继承A 和 B 和两者 都有一个函数say_hello。而B 继承自A。

您不能乘以从基类继承后跟派生类
定义一个满足通常 MRO 约束/保证的一致 MRO 是不可能的。如上所述here

您现在调用super(D, self).say_hello() 并且python 不知道选择哪个say_hello。
A 或B？！

这个例子可以工作：

class D(A): #D only inherits A not A and B
    def say_hello(self):
        super(D, self).say_hello()
        print 'D says hello'


DD = D()
DD.say_hello()

#output
>>>A says hello
>>>D says hello


#There are 2 connections to As say_hello
    A-----
   / \   |
  B   C  |
  |     /
  \    / 
    D

PS：请使用“self”作为第一个参数的名称

更新： 如果继承看起来像这样，它将选择Assay_hello

class A(object):
    def say_hello(cls):
        print 'A says hello'


class B():
     def say_hello(cls):
        print 'B says hello'


class C(B):
    def say_hello(cls):
        super(C, cls).say_hello()
        print 'C says hello'


class D(A, C):
    def say_hello(self):
        super(D, self).say_hello()
        print 'D says hello'


DD = D()
DD.say_hello()

继承树：

    A
  /
  |   B
  |   |
  |   C
  \   / 
    D

Python 现在选择最不专业的 say_hello，例如A.