尝试“钻石形状"问题时，带有OOP的Python在这里发生了什么 [英] What is happening here in Python with OOPs while trying Diamond Shape problem

问题描述

我正在用python学习OOP.在下面的代码中创建，以在多个继承中复制菱形问题.我正在jupyter笔记本中运行以下代码，并且输出是同时生成的.

I am learning OOPs with python. created below code to replicate the diamond shape problem in multiple inheritence. I am running the below code in jupyter notebook and output is generated at same.

class parent:
    def __init__(self):
        self.a=2
        self.b=4
    def form1(self): 
        print("calling parent from1")
        print('p',self.a+self.b)

class child1(parent):
    def __init__(self):
        self.a=50
        self.b=4
    def form1(self):
        print('bye',self.a-self.b)
    def callchildform1(self):
        print("calling parent from child1")
        super().form1()

class child2(parent):
    def __init__(self):
        self.a=3
        self.b=4
    def form1(self):
        print('hi',self.a*self.b)
    def callchildform1(self):
        print("calling parent from child2")
        super().form1()

class grandchild(child1,child2):
    def __init__(self):
        self.a=10
        self.b=4
    def callingparent(self):
        super().form1()

g=grandchild()
g.form1()
g.callchildform1()
g.callingparent()

输出如下

bye 6
calling parent from child1
hi 40
bye 6

我两次都可以理解"bye 6"输出，但是它是如何打印"hi 40"的.我是新来的，所以任何人都可以解释这里发生的事情.

I can understand the "bye 6" output both the times but how it is printing "hi 40". I am new so anybody can explain what is happening here.

推荐答案

您可能会找到信息丰富的类的__mro__属性.在这里，MRO代表 M ethod R 解决方案 O rder.

You may find the __mro__ attribute of a class informative. Here, MRO stands for Method Resolution Order.

请考虑对您的代码进行以下修改:

Consider this modification to your code:

class Parent:
    def __init__(self):
        self.a = 2
        self.b = 4

    def print_name(self):
        print("parent")

    def form1(self):
        print("calling parent form1")
        print('p', self.a + self.b)


class Child1(Parent):
    def __init__(self):
        self.a = 50
        self.b = 4

    def print_name(self):
        print("child1")

    def print_super_name(self):
        super().print_name()

    def form1(self):
        print('bye', self.a - self.b)

    def callchildform1(self):
        print("calling parent from child1")
        super().form1()


class Child2(Parent):
    def __init__(self):
        self.a = 3
        self.b = 4

    def print_name(self):
        print("child2")

    def form1(self):
        print('hi', self.a * self.b)

    def callchildform1(self):
        print("calling parent from child2")
        super().form1()


class Grandchild(Child1, Child2):
    def __init__(self):
        self.a = 10
        self.b = 4

    def print_name(self):
        print("grandchild")

    def print_super_name(self):
        super().print_name()

    def print_super_super_name(self):
        super().print_super_name()

    def callingparent(self):
        super().form1()


g = Grandchild()
print("When I print the name of my class it is:")
g.print_name()
print("When I print my superclass name, it is:")
g.print_super_name()
print("When I print the name of the superclass of my superclass, it is:")
g.print_super_super_name()
print("When you call methods on me, they will be executed from my class and my parent classes in the following order:")
print(Grandchild.__mro__)
g.form1()
g.callchildform1()
g.callingparent()

输出为:

When I print the name of my class it is:
grandchild
When I print my superclass name, it is:
child1
When I print the name of the superclass of my superclass, it is:
child2
When you call methods on me, they will be executed from my class and my parent classes in the following order:
(<class '__main__.Grandchild'>, <class '__main__.Child1'>, <class '__main__.Child2'>, <class '__main__.Parent'>, <class 'object'>)
bye 6
calling parent from child1
hi 40
bye 6

运行g.callchildform1()时，Python在Grandchild中查找callchildform1的定义.它不在那里，所以下一个看起来是Child1.您可以从示例和方法解析顺序中看到，当Grandchild的实例调用Child1中定义的方法(该方法调用super())时，对被调用方法的搜索将从Child2开始.

When you run g.callchildform1() Python looks for the definition of callchildform1 in Grandchild. It isn't there, so the next place it looks is Child1. You can see from the example and from the method resolution order that when an instance of Grandchild calls a method defined in Child1 which calls super(), the search for the called method will begin in Child2.

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