对象

1、举例：可以拿球举例，可以操作一个球，比如捡球、抛球、踢球、或者充气，这些称之为动作，还可以通过指出球的颜色、大小和重量来描述一个球。这些称为一个球的属性。

2、对象包括两个方面：可以对他做什么（动作）：方法；如何描述（属性或特性）：属性

3、在python 中，一个对象的特征（或你知道的事情），称为属性，动作（能够对对象做的操作）称为方法。

球的属性：ball.color  ball.size ball.weight   球的方法：ball.kick() ball.throw() ball.inflat()

4、什么是属性：属性就是你所知道关于球的所有方面，球的属性就是一些信息（数字，字符串等），其实就是变量，包含在对象中的变量。

print ball.size
ball.color = "red"
mycolor = ball.color
myball.color = ball.color

5、什么是方法：方法就是可以对对象进行的操作，他们是一些代码块，可以调用代码块完成一些工作，方法就是包含在对象里的函数。

6、创建对象的2个步骤：1、第一步：定义对象看上去什么样，会做什么，也就是它的属性和方法。只是创建一个蓝图，对象的描述和蓝图称为一个类。

                                        2、第二步：使用类来建立一个真正的对象。这个对象称为这个类的一个实例。

class ball:
    def bounce(self):
        if self.direction == "down":
           self.direction =="up"              # 创建一个类

myball = ball()                               # 建立类的实例
myball.direction = "down"
myball.color = "red"
myball.size = "small"

print("I just created a ball .")              # 打印对象的属性
print("my ball is ",myball.size)
print("my ball is ",myball.color)
print("My ball's direction is ",myball.direction)
print("Now I'M going to bounce the ball ")
myball.bounce()                                # 使用一个方法 
print("Now the ball's direction is ",myball.direction)

7、初始化对象：名为__init__

class ball:
    def __init__(self,color,size,direction):      # 这里__init__ 为两条下划线
        self.color = color
        self.size = size
        self.direction = direction

    def bounce(self):
        if self.direction == "down":
            self.direction == "up"

myball = ball("red","small","down")               # 属性作为__int__()的参数传入
print("I just created a ball .")
print("my ball is ",myball.size)
print("my ball is ",myball.color)
print("My ball's direction is ",myball.direction)
print
myball.bounce()
print("Now the ball's direction is ",myball.direction)

8、__str__(),它会告诉python打印（print）一个对象时具体显示什么内容。

# 使用__str__()改变打印对象

class ball:
    def __init__(self,color,size,direction):
        self.color = color
        self.size = size
        self.direction = direction

    def __str__(self):
        msg = "HI , I'M A " + self.size + self.color + "ball"
        return msg

myball = ball("red","small","down")
print(myball)

9、self self参数会告诉方法哪个对象调用它，称为实例引用

10、热狗程序

class HotDog:
    def __init__(self):
        self.cooked_level = 0
        self.cooked_string = "Raw"
        self.condiments = []

    def cook(self,time):
        self.cooked_level = self.cooked_level + time
        if self.cooked_level > 8:
            self.cooked_string = "Charocal"
        elif self.cooked_level >5:
            self.cooked_string = "well-done"
        elif self.cooked_level > 3:
            self.cooked_string = "medium"
        else:
            self.cooked_string = "Raw"
mydog = HotDog()
print ("mydog cooked_level : ",mydog.cooked_level)             # 创建一个实例，名为hotdog 烤前的状态
print("mydog cooked_string : ",mydog.cooked_string)
print("mydog condiments : " , mydog.condiments)
print("i'm now going to cook the hot dog")
mydog.cook(4)                                                  # 用cook()方法，打印烤后的状态
print("mydog cookde_level : ",mydog.cooked_level)
print("mydog cooked_string : ",mydog.cooked_string)

11、包含cook(),add_condiment()和__str__()的Hot dog类

class Hotdog:
    def __init__(self):                             # 初始化对象
        self.cooked_level = 0
        self.cooked_string = "Raw"
        self.condiments = []
    def __str__(self):                             #定义新的__str__ 方法 （）
        msg = " hot dog "
        if len(self.condiments) > 0:
            msg = msg + " with "
        for i in self.condiments:           # 循环列表的数据
            msg = msg + i + ","
        msg = msg.strip(",")
        msg = self.cooked_string + "" + msg + "."       # __str__  用msg 作为返回  更好地打印我们的对象
        return  msg
    def cook(self,time):
        self.cooked_level = self.cooked_level + time
        if self.cooked_level > 8:
            self.cooked_string = "Charocal"
        elif self.cooked_level > 5:
            self.cooked_string = "well-done"
        elif self.cooked_level > 3:
            self.cooked_string = "medium"
        else:
            self.cooked_string = "Raw"
    def addCondiment(self,condiment):
        self.condiments.append(condiment)
mydog = Hotdog()
print(mydog)
print("cooking hot dog for 4 minutes ...")
mydog.cook(4)
print(mydog)
print("cooking hot dog for 3 minutes ...")
mydog.cook(3)
print(mydog)
print("what happens if i cook it for 10  more minutes ? ")
mydog.cook(10)
print("now , i'm going to add some stuff on my hot dog ")
mydog.addCondiment("Ketchuo")
mydog.addCondiment("mustard")
print (mydog)

12、对象的多态性

#   对象的多态性 -同一个方法，不同的行为

class Triangle:
    def __init__(self,width,height):
        self.width = width
        self.height = height
    def getArea(self):
        area = self.width * self.width / 2.0
        return area
class Square:
    def __init__(self,size):
        self.size = size
    def getArea(self):
        area = self.size * self.size
        return area
myTriangle =Triangle(4,5)                  # 创建2个 实例
mySqure = Square(7)
myTriangle.getArea()
print(myTriangle)
mySqure.getArea()
print(mySqure)                      # 如何用__str__（） 方法正常打印输出？

13、对象的继承性 

对象的继承性

class Gameobject:
    def __init__(self,name):
        self.name = name
    def pickup(self):
        pass
        # put code here to add the project
        # to the player's collection
class Coin(Gameobject):
    def __init__(self,value):
        Gameobject.__init__(self,value)
        self.value = value
    def spend(self,buyer,seller):
        pass
        # put code here to remove the coin
        # from the buyer's money and
        # add it to the seller's money

14、课后习题

# 为BankAccount 建立一个类定义。它有的属性为：账户名（字符串），账号（一个字符串或整数），余额（浮点数），另外还需用方法显示余额、存钱、取钱
# 作者：wang cheng  hua

class BankAccount:
    def __init__(self,acct_number,acct_name):
        self.acct_number = acct_number
        self.acct_name = acct_name
        self.balance = 0.0
    def displayBalance(self):
        print("the account balance is ",self.balance)
    def deposit(self,amount):
        self.balance =self.balance + amount
        print("you depositde  ",amount)
        print("the new balance is ",self.balance)
    def withdraw(self,amount):
        if self.balance >= amount:
           self.balance =self.balance -amount
           print("you withdrawde ",amount)
           print("the new balance ",self.balance)
        else:
            print("you have tried to withdraw ",amount)
            print(" the account balance is ",self.balance)
            print("withdrawal denied . not enough funds ")

myaccount =BankAccount('440303201','wang')
myaccount.displayBalance()
myaccount.deposit(500)
myaccount.withdraw(300)
myaccount.withdraw(300)


# 为BankAccount 建立一个利息的类，名为interestAccount ,为BanKAccount 的子类 （会继承BankAccount 的属性和方法）
# 作者：wang cheng  hua
class InterestAccount(BankAccount):
    def __init__(self,acct_number,acct_name,rate):
        BankAccount.__init__(self,acct_number,acct_name)
        self.rate = rate
    def addInterest(self):
        interst = self.balance * self.rate
        print("adding the interst in the account ,",self.rate * 100,"precent")
        self.deposit(interst)
myaccount = InterestAccount("230333","wang",0.11)
print("the account number is : ",myaccount.acct_number)
print("the account name is :",myaccount.acct_name)
myaccount.displayBalance()
myaccount.deposit(34.52)
myaccount.addInterest()