The first notes of 2022 Python winter vacation advanced training

• class (Class):  A collection of objects with the same properties and methods . It defines the properties and methods that are common to each object in the collection . Object is an instance of a class .
• Class variables ： Class variables are common to the entire instantiated object . Class variables are defined in the class and outside the function body . Class variables are usually not used as instance variables .
• Data member ： Class variable or instance variable , Used to process data related to classes and their instance objects .
• Method rewriting ： If the method inherited from the parent class does not meet the needs of the child class , It can be rewritten , This process is called method coverage （override）, Also known as method rewriting .
• local variable ： Variables defined in methods , Class that only works on the current instance .
• Instance variables ： In the declaration of a class , Properties are represented by variables . This variable is called instance variable , It is declared inside the class declaration but outside the other member methods of the class .
• Inherit ： That is, a derived class （derived class） Inherited base class （base class） Fields and methods for . Inheritance also allows the object of a derived class to be treated as a base class object . for example , There is such a design ： One Dog Object of type derived from Animal class , This is a simulation " It's a （is-a）" Relationship （ Case diagram ,Dog It's a Animal）.
• Instantiation ： Create an instance of a class , Class specific objects .
• Method ： Functions defined in class .
• object ： Data structure instance defined by class . Object contains two data members （ Class variables and instance variables ） And methods .

•  Example ：
  # Create parent class
  class Passengercar(object):
  def __init__(self,name,weight,drive): # Definition __init__ Method
  self.name = name # Pass values to parameters
  self.weight = weight
  self.drive = drive
  def __print__(self): # Define methods Print car Class properties
  print ("Name:",self.name,"Weight : ", self.weight, ", Drive: ", self.drive)
  # Create subclass
  class bus(Passengercar): # Inherited parent class （） Inside is the name of the parent class
  def __init__(self,name,weight,drive): # Definition __init__ Method
  super(bus, self).__init__(name,weight,drive) # Inherit the properties of the parent class
  

• import Demo02 # Test class import
  bus1 = Demo02.bus(" Dongfeng Road 28 Road bus ", "3000kg", " automatic ") # Assign a value to an object
  bus1.__print__() # call print Method 

• from Demo02 import Class name     # Or import the class directly   
• If you inherit two parent classes at the same time , Both superclasses have the same method name , Give priority to the methods written in the previous parent class when inheriting .

Such as ：from Mother import Mother

       from Father import Father

        class Child(Father,mother):

                def __init__(self,mother,father)

                        Father.__intit__(self,father)

                        Mother.__init__(self,faceValue)

Calling the same named method takes precedence over Father Class method

website ：https://www.runoob.com/python/python-object.html Video tutorial （ Study P1\P2\P3）：https://www.bilibili.com/video/BV1na4y1x7Si?p=1 polymorphic CSDN：https://blog.csdn.net/weixin_44695969/article/details/92175840

(30 Bar message ) Python How to understand polymorphism in ？_tigerlib The blog of -CSDN Blog _python polymorphic