Super calling details in multiple inheritance

Note: Python 3 is used as the operating environment here, and the example is taken from Chapter 8 of "python cookbook".

In python, if a subclass wants to initialize the parent class, there are two main methods. The first is to directly pass the parent class name, and the second is to use the super method. There is no difference between the two in single inheritance, but there are some subtle differences that need to be paid attention to in multiple inheritance. Example explanation is the last word!
1. The case of using the parent class name:

Python code

class Base:

def __init__(self):

print('Base.__init__')

class A (Base):

def __init__(self):

                                                        use using using using           use using ‐                 ‐                           use using     out out out out out of ’s to  def __init__(self)’s to be __init__(self’ be-to-be--

             Base.__init__(self) " B.__init__(self)

print( 'C.__init__')

Python code

>>> c = C()

Base.__init__

A.__init__

Base .__init__

B.__init__

C.__init__

>>>

It can be seen that the Base class is called twice. This must not be the result we want in many cases, so we can consider using the super method at this time.

Python code

class Base:

def __init__(self):

print('Base.__init__')

class A (Base):

def __init__(self):

                                                                                                                                                                                                                                                 

              super().__init__( )

                                                                                                                                                                                                ) to super() here

At this time, the output of Class C is instantiated at this time:

It can be seen that the Base class is only called once! But unfortunately, this is not what prompted me to write this blog record, because if you observe carefully, although the Base class is indeed called only once as expected, have you noticed that "B.__init__" is output first and then Just output "A.__init__"? And why does this cause Base to be initialized only once? You must be a little confused too, right? In fact, all this is "blamed" on the calling process of super during multiple inheritance. When python implements a class (not just inheritance), it will generate a method to generate a parsing order list, which can be viewed through the class attribute __mro__, as in this example: