[Basic 6] - encapsulation and inheritance of classes, objects and classes

Case study ： Bank card

Write a bank card ：
attribute ： Name of Bank , Card number , password , full name , balance
Method : Sign in , deposit

class Card():
    def __init__(self,cnum,cpwd,cname,cbalance):
        self.bankName = "python Bank "
        self.cnum = cnum
        self.cpwd = cpwd
        self.cname = cname
        self.cbalance = cbalance

    def login(self):
        num = input(" Please enter the card number ：")
        pwd = input(" Please input a password :")
        if num==self.cnum and pwd==self.cpwd:
            print(" Verify success ！")
            return "ok"
        else:
            print(" Validation failed ！")
            return "no"
    def deposit(self):
        r=self.login()# Call other methods in the question part of the class , Use self As object name 
        if r=="ok":
            money=float(input(" Please enter the deposit amount ："))
            self.cbalance+=money
            print(" Deposit success ！ Deposit in ",money," element ！ balance ",self.cbalance," element ！")

c1=Card("1001","123"," Zhang San ",1000)
c2=Card("1002","123"," Li Si ",5000)

c2.deposit()

Please enter the card number ：1002
Please input a password :123
Verify success ！
Please enter the deposit amount ：1500
Deposit success ！ Deposit in 1500.0 element ！ balance 6500.0 element ！

One 、 Class encapsulation

Privatize properties or attributes in a class , Privatized properties and methods can only be called inside a class
take Above Private property self.cbalance = cbalance Change it to self.__cbalance = cbalance, The running result is ：

AttributeError: ‘Card’ object has no attribute ‘__cbalance’

thus it can be seen , Yes, it is encapsulation , Become private attribute , Cannot directly access

• Encapsulation can restrict access to properties or methods

    class Card():
    def __init__(self,cnum,cpwd,cname,cbalance):
        self.bankName = "python Bank "
        self.cnum = cnum
        self.cpwd = cpwd
        self.cname = cname
        self.__cbalance = cbalance

    def login(self):
        num = input(" Please enter the card number ：")
        pwd = input(" Please input a password :")
        if num==self.cnum and pwd==self.cpwd:
            print(" Verify success ！")
            return "ok"
        else:
            print(" Validation failed ！")
            return "no"

    def showBalance(self):
    	# Restrict access to properties or methods 
        r = self.login()
        if r == "ok":
            print(" balance :",self.__cbalance," element ！")

    def deposit(self):
        r=self.login()# Call other methods inside the class , Use self As object name 
        if r=="ok":
            money=float(input(" Please enter the deposit amount ："))
            self.cbalance+=money
            print(" Deposit success ！ Deposit in ",money," element ！ balance ",self.cbalance," element ！")

c1=Card("1001","123"," Zhang San ",1000)
c2=Card("1002","123"," Li Si ",5000)

c2.showBalance()

Please enter the card number ：1002
Please input a password :123
Verify success ！
balance : 5000 element ！

• Private method
  take Above Private method def login(self): Change it to def __login(self):, Can only be called inside a class , It can improve the security of classes

Two 、 Class inheritance

One class inherits another class , Automatically own the properties and methods of this class
Parent class – Subclass

• Parent class ： Define common properties and methods in multiple classes .
• stay Python in , A parent class can have more than one subclass ; A subclass can have more than one parent class （ special ）（ Multiple inheritance ）
• object: The ultimate parent of all classes

# Parent class ： Define common properties and methods in multiple classes 
# stay Python in , A parent class can have more than one subclass ; A subclass can have more than one parent class （ special ）（ Multiple inheritance ）
#object: The ultimate parent of all classes 
class Animal():
    def __init__(self,color,age):
        print("Animal The initialization method is called ！")
        self.color=color
        self.age=age
    def eat(self):
        print(" Animals are eating ！")
    def run(self):
        print(" Animals are running ！")

class Cat(Animal):# Subclass （ Parent class ）
    pass

class Dog(Animal):
    pass

class Bird(Animal):
    def fly(self):
        print(" Birds are flying ！")

#------------------------------
c1=Cat(" orange ",2)
c1.eat()

b1=Bird(" orange ",2)
b1.fly()

Animal The initialization method is called ！
Animals are eating ！
Animal The initialization method is called ！
Birds are flying ！