Python 3.x Learning note 10 (destructor and inheritance)

1. Use of class variables:
Common properties for everyone, save overhead (memory)

2. Destructors
Performed when an instance is released and destroyed, usually for some finishing touches, such as closing some database links and opening temporary files

3. Private methods
The two underscore begins with the declaration that the method is a private method and cannot be called outside of a class.

4. Private properties
The two underscore begins with the declaration that the property is private and cannot be used outside of the class or accessed directly.

5.

When inheriting, rewrite the constructor to write all the parameters of the parent class once plus the child class variable, then call the parent class, and then add the instantiation variable of the subclass.

6.
The python2.x Classic class is inherited by depth, and the new class is inherited by the breadth of the first.

python3.x Classic classes and modern classes are all inherited by breadth first.

Practice

1 #Parent Class 12 classPerson (object):#New Style3 4     def __init__(self,name,age):5         #constructor Function6Self.name = Name#instantiate a variable (static property), scoped to instantiate itself7Self.age = Age8Self.friends = []9 Ten     defEat (self):#class method functionality (Dynamic properties) One         Print('%s'll eat something!'%self.name) A  -     defRun (self): -         Print('%s'll runing!'%self.name) the  -     defSleep (self): -         Print('%s'll sleep!'%self.name) -  + #Parent Class 2 - classRelation (object): +     defmake_friends (self,obj): A         Print('%s make friend with%s'%(self.name,obj.name)) atSelf.friends.append (obj)#the argument here is obj, in this example, obj is both a W1 -  -  - #sub-class - classMan (person,relation):#Multiple Inheritance -     def __init__(Self,name,age,money):#overriding Constructors in         #person.__init__ (Self,name,age,money) #经典写法 -Super (Man,self).__init__(Name,age)#new style of writing, it is suggested to use this toSelf.money = Money +  -     defPiao (self): the         Print('%s is piaoing ....'%self.name) *  $ Panax Notoginseng #sub-class - classWoman (person,relation):#Multiple Inheritance the     defPiao (self): +         Print('%s is piaoing ....'%self.name) A  theM1 = Man ('Zhang San', 20,10) +  -W1 = Woman ('Lili'21st) $  $ m1.make_friends (W1) - Print(M1.friends[0].name) - Print(m1.friends[0].age) the  - #M1.piao ()Wuyi #m1.eat () the #M1.run () - #M1.sleep ()

Python 3.x Learning note 10 (destructor and inheritance)