Class

• 私有方法
• __del__方法
• 繼承；多繼承
• 重寫；
• 多態；
• 類屬性；實例屬性；
• 類方法；實例方法；靜態方法；
• __new__方法
• 建立單例對象
• 異常
• 模塊自我測試和調用相沖突的解決辦法
• 設計4s店類(pass)

 

私有方法：

class Dog:

   #私有方法

   def __send_msg(self):

      print('------正在發送短信------')

   def send_msg(self,money):

      if money > 10000:

         self.__send_msg()

      else:

         print('-----您的餘額不足，請充值-----')

 

dog = Dog()

dog.send_msg(5000)

__del__方法:

class Dog:

   def __del__(self):

      print('-----英雄over-----')

dog1 = Dog()

dog2 = dog1

 

del dog1 #此時不會調用__del__方法，由於這個對象還有其餘變量指向它，即引用計算不是0

del dog2 #此時會調用__del__方法，由於已經沒有變量指向它了

print('=================')

#若是在程序結束時，有些對象還存在，那麼python解釋器會自動調用它們的__del__方法來完成清理工做

inherit:

#INHERIT_ONE

class Anaimal:

    def eat(self):

        print('-----eat-----')

    def drink(self):

        print('-----drink-----')

    def play(self):

        print('-----play-----')

    def run(self):

        print('-----run-----')

class Dog(Anaimal):

    def bark(self):

        print('-----bark-----')

class Cat(Anaimal):

    def catch(self):

        print('-----catch-----')

 

tom = Cat()

tom.eat()

tom.catch()

#if used tom.bark, you will get a error.

#INHERIT_TWO

class Anaimal:

    def eat(self):

        print('-----eat-----')

    def drink(self):

        print('-----drink-----')

    def play(self):

        print('-----play-----')

    def run(self):

        print('-----run-----')

class Cat(Anaimal):

    def catch(self):

        print('-----catch-----')

class Animation_Cat(Cat):

    def speak(self):

        print('-----speak-----')

 

tom = Animation_Cat()

tom.eat()

tom.catch()

tom.speak()

#Tom can use Anaimal, Cat and Animation_Cat.  

#INHERIT_ISSUE

class Anaimal:

     def __init__(self):

        self.num = 'I can inherit!'

        self.__num = 1 #私有屬性

    def __swim(self): #私有方法

        print('-----swim-----')

    def run(self):

        self.__swim() #公有方法下的私有屬性

        print(self.__num) #公有方法下的私有方法

class Cat(Anaimal):

    #Attention:若是是這裏的 公有方法下的私有屬性或方法會報錯，緣由能夠走一遍循環：先找本身的方法，找不到的話，若是是公有方法往父類上找，私有方法由於不能被繼承，直接報錯。

    pass

 

tom = Cat()

#tom.__swim() #AttributeError:私有method can't be inherit!

#print(tom.__num) #AttributeError:私有屬性 can't be inherit!

print(tom.num)

tom.run() #包含在共有屬性中的私有方法和私有屬性能夠被繼承！

 

#Conclusion:通常來講，公有屬性和公有方法會被繼承，而私有屬性和私有方法卻不會被繼承。可是存在兩種特殊狀況：若是是父類的公有方法下調用私有屬性和私有方法會被繼承。若是是子類的公有方法下調用私有屬性和私有方法會報錯

#Conclusion:The general rule is that common attributes and common methods are inherited, private attributes and private methods are not inherited. But there are two kinds of special cases: ① If it is public methods of the parent with private property and private methods will be inherited. ② If it is public methods of the son with private property and private methods will not be inherited.

#Multiple inheritance(多繼承)

class base(object):

    def test(self):

        print('-----test-----')

class A(base):

    def test1(self):

        print('-----test1-----')

class B(base):

    def test2(self):

        print('-----test2-----')

class C(A,B):

    pass

 

tom = C()

tom.test()

tom.test1()

tom.test2()

 

#多繼承的注意點：print(tom.__mro__)

#會打印調用一個方法時搜索的順序（C3算法）

#儘可能避免在類中出現相同的方法

REWRITE:

#REWRITE_ONE

class Anaimal:

    def eat(self):

        print('-----eat-----')

    def drink(self):

        print('-----drink-----')

    def play(self):

        print('-----play-----')

    def run(self):

        print('-----run-----')

class Cat(Anaimal):

    def catch(self):

        print('-----catch-----')

class Animation_Cat(Cat):

    def speak(self):

        print('-----speak-----')

     def catch(self):

        #if you rewrite 'catch', his father will be cover.

        print('-----not catch-----')

    

tom = Animation_Cat()

tom.eat()

tom.catch()

tom.speak()

#REWRITE_TWO

class Anaimal:

    def eat(self):

        print('-----eat-----')

    def drink(self):

        print('-----drink-----')

    def play(self):

        print('-----play-----')

    def run(self):

        print('-----run-----')

class Cat(Anaimal):

    def catch(self):

        print('-----catch-----')

class Animation_Cat(Cat):

    def speak(self):

        print('-----speak-----')

    def catch(self):

        print('-----not catch-----')

          #if you want to call son's catch first, then call father's catch.

        #the first method

        Cat.catch(self)

        #the second method

        super().catch()

 

tom = Animation_Cat()

tom.catch()

polymorphism(多態):

class Dog(object):

    def introduce(self):

        print('你們好，我是xxx')

class Xiaotq(Dog):

    def introduce(self):

        print('hello,我是神犬')

def function(temp):

    #只有在運行的時候才肯定屬於誰

    temp.introduce()

 

dog1 = Dog()

dog2 = Xiaotq()

function(dog1)

function(dog2)

類屬性和示例屬性：

class Tool(object):

     #類屬性

    num = 0

    def __init__(self, new_name):

        #實例屬性

        self.name = new_name

        #對類屬性+1

        Tool.num += 1

 

tool1 = Tool('鐵鍬')

tool2 = Tool('工兵鏟')

tool3 = Tool('水桶')

print(Tool.num)

__new__方法：

class Cat(object):

    def __init__(self):

        print('----init方法----')

    def __del__(self):

        print('----del方法----')

    def __str__(self):

        print('----str方法----')

    def __new__(cls):

        print('----new方法----,,,')

        return object.__new__(cls)

 

tom = Cat()

#並無很懂，可是流程是先調用__new__，接收到它的返回值以後，調用__init__方法，而不是從__new__中調用__init__方法

建立單例對象：

class Cat(object):

    __instance = None

    #建立一個私有類屬性

    def __new__(cls):

        if cls.__instance == None:

            cls.__instance = object.__new__(cls)

            return cls.__instance

        else:

            #返回上一次建立的對象的引用

            return cls.__instance

 

tom = Cat()

print(id(tom))

cat = Cat()

print(id(cat))

#只初始化一次對象

class Cat(object):

    __instance = None

    #建立一個私有類屬性

    def __new__(cls, name):

        if cls.__instance == None:

            cls.__instance = object.__new__(cls)

            return cls.__instance

        else:

            #返回上一次建立的對象的引用

            return cls.__instance

    def __init__(self, name):

        self.name = name

 

tom = Cat('湯姆')

print(id(tom))

print(tom.name)

cat = Cat('小貓')

print(id(cat))

print(cat.name)

#只初始化一次對象2

class Cat(object):

    __instance = None

    __init_flag = False

    #建立一個私有類屬性

    def __new__(cls, name):

        if cls.__instance == None:

            cls.__instance = object.__new__(cls)

            return cls.__instance

        else:

            #返回上一次建立的對象的引用

            return cls.__instance

    def __init__(self, name):

        if Cat.__init_flag == False:

            self.name = name

            Cat.__init_flag = True

 

tom = Cat('湯姆')

print(id(tom))

print(tom.name)

cat = Cat('小貓')

print(id(cat))

print(cat.name)

異常：

#異常處理-基本功能

try:

    print(un)

    open('xxx.txt')

except (NameError,FileNotFoundError):

    print('捕獲到異常')

except Exception as result:

    #Exception是全部異常的總稱

    print('捕獲到其餘異常')

    print('result')

else:

    print('沒有異常纔會執行的功能')

finally:

    #不管上面是否出現異常，都會執行finally

    print('-----finally----')

    f.close()

    print('文件關閉')

#異常的傳遞

def test1():

    print(num)

def test2():

    test1()

def test3():

    try:

        test2()

    except Exception as result:

        print('已捕獲到異常，異常信息爲：(%s)'%result)

 

test3()

#拋出自定義異常

class ShortInputException(Exception):

    #自定義的異常類

    def __init__(self, length, atleast):

        #super().__init__()

        self.length = length

        self.atleast = atleast

 

def main():

    try:

        s = input('請輸入字符：')

        if len(s) < 3:

            raise ShortInputException(len(s),3)

    except ShortInputException as result:

        print('ShortInputException:輸入的長度是%d,長度至少是%d'%(result.length,result.atleast))

    else:

        print('noerror')

 

main()

#異常處理中拋出異常

class Test(object):

    def __init__(self, switch):

        self.switch = switch #開關

    def calc(self, a, b):

        try:

            return a/b

        except Exception as result:

            if self.switch:

                print('捕獲開啓，已經捕獲到了異常，信息以下：')

                print(result)

            else:

                #從新拋出這個異常，此時就不會被這個異常處理給捕獲到，從而觸發默認的異常處理

                raise

 

a = Test(True)

a.calc(11,0)

print('---------------分割線--------------------')

a.switch = False

a.calc(11,0)

#模塊自我測試和調用相沖突的解決辦法

def test1():

    print('-----test1-----')

def test2():

    print('-----test2-----')

def main():

        test1()

        test2()

if __name__ == '__main__':

    main()