# 8_Object-Oriented Programming --- ### 物件導向 Object-oriented ##### 物件導向程式設計(Object-oriented programming, OOP) * 類別 ( Class ) * 物件 ( Object ) * 屬性 ( Attribute ) * 方法 ( Method ) * 建構子 ( Constructor ) --- ## 類別 Class #### <font color='red'>Classes</font> provide a means of bundling data and functionality together. Creating a new class creates a new type of <font color='red'>object</font>, allowing new <font color='red'>instances</font> of that type to be made #### Class 提供了一種結合資料與功能的手段。建立一個 class 將會新增一個<font color='red'>物件</font>的型別，並且允許建立該型別的新<font color='red'>實例</font>。 --- ### 類別說明 :::info 一個抽象的概念 -- 車子，人類，大象，蛋糕 ... * 車子 是 ... 有 ... 可以(會） ... * 人類 是 ... 有 ... 可以(會） ... * 大象 是 ... 有 ... 可以(會） ... * 蛋糕 是 ... 有 ... 可以(會） ... ::: --- ### 類別 Class :::info 車子 * 是本身具有動力得以驅動前進，具有兩輪或以上以原動機驅動 * 有廠牌，價格，動力來源，車牌號碼 ... * 可以定速巡航，車道維持輔助 ... ::: :::success **類別** **有**靜態資料 -- <font color='blue'>**屬性 (Attribute) 也就是變數**</font> **可以**操作動作 -- <font color='blue'>**方法(Method) 也就是函式**</font> ::: --- #### 定義類別 Class definition ```python= class ClassName: ... ... ``` #### 建立物件 Object instantiation ```python= object = ClassName() ``` --- #### 車子類別 ```python= # Define a car Class class Car: pass # nothing to do car1 = Car() # Car instance / car object car2 = Car() # Car instance / car object ```  --- #### 實例變數 (instance variable) ###### 每一個實例有自已的屬性資料 ```python= # Define a car Class class Car: pass # nothing to do car1 = Car() # Car instance / car object car1.brand = "Toyota" car2 = Car() # Car instance / car object car2.weight = 450 ```  --- ### \_\_init\_\_() 特別方法 ###### 建立<font color=#FF6600>預設</font>實例變數 :::info __init__(self [,... ]): constructor self is the instance itself ::: ```python= #initial the instace variable withr default value def __init__(self): self.attribute = "default value" #initial the instace variable with user defined value def __init__(self, attr1): self.attribute = attr ``` --- #### 定義車子類別 + 預設實例變數 ```python= # Define a car Class class Car: # Constructor def __init__(self): # initial instance variable self.brand = "Toyota" ```  --- #### 建立物件 車子類別 + 預設實例變數 ```python=預設實例變數 class Car: # Constructor def __init__(self): # initial instance variable self.brand = "Toyota" car1 = Car() ```  --- #### 建立物件 車子類別 + <font color=#FF6600>自訂</font>預設實例變數 ```python= class Car: def __init__(self, brand): self.brand = brand car1 = Car("Toyota") car2 = Car("Tesla") ```  --- #### 物件使用屬性 ( Access attribute) :::info object.attribute_name ::: ```python= class Car: def __init__(self, brand): self.brand = brand car1 = Car("Tesla") # print car brand print(f"car1.brand is {car1.brand}") ``` ```shell car1.brand is Tesla ```  --- #### 自訂預設實例變數的<font color=#FF6600>預設值</font> ```python= class Car: # sepacial method with default Toyota brand def __init__(self, brand = "Toyota"): # initial instance variable brand self.brand = brand ```  --- #### 自訂預設實例變數<font color=#FF6600>使用</font>預設值產生物件 ```python= class Car: def __init__(self, brand = "Toyota"): self.brand = brand car1 = Car() # No brand --> brand is Toyota print(f"car1.brandis {car1.brand}") ``` ```shell car1.brand is Toyota ```  --- #### 自訂預設實例變數<font color=#FF6600>不使用</font>預設值產生物件 ```python= class Car: def __init__(self, brand = "Toyota"): self.brand = brand car1 = Car("Tesla") # brand is Tesla print(f"car1.brand is {car1.brand}") ``` ```shell car1.brand is Tesla ```  --- #### 實例方法 (instance method) :::info 類別中沒有加任何裝飾詞(Decorator)的方法(Method)-也就是類別中的函式 ::: ```python= Class ClassName: def method(self[,...]): ... ... ``` --- #### 車子類別 + 實例方法 ```python= class Car: def __init__(self, brand = "Toyota"): self.brand = brand # 實例方法 instance method def info(self): return f"This car is {self.brand} brand)" ```  --- #### 物件使用實例方法 ( Access instance method) :::info object.method_name ::: ```python= class Car: def __init__(self, brand = "Toyota"): self.brand = brand def info(self): return f"This car is {self.brand} brand" car1 = Car("Tesla") print(car1.info()) ``` ```shell This car is Tesla brand) ``` --- ##### class diagram  --- ### 類別變數 Class Variable ###### 類別中直接定義的變數，所有實例共享的變數 ```python= Class ClassName: attribute = xxx ... ... ``` --- #### 車子類別 + 類別變數 ```python= class Car: chinese_name = "汽車" # 類別變數 class variable def __init__(self, brand = "Toyota"): self.brand = brand def info(self): return f"This {self.brand} is {self.chinese_name}" car1 = Car("Tesla") print(car1.info()) car2 = Car("Toyota") print(car2.info()) ``` ```shell This Tesla is 汽車 This Toyota is 汽車 ``` :::danger 兩台車 chinese_name 都一樣 ！！！ ::: --- ##### class diagram  --- #### __str__(self) special method ###### 類別的預設方法之一，物件的字串表達形式 ``` print(object) --> python call object.__str__(self) ```` ```python= class Car: status = "Good" # class attribute def __init__(self, brand = "Toyota"): self.brand = brand def __str__(self): return f"Car class status {self.status} from __str__" def info(self): return f"This {self.brand} is {self.status}" car1 = Car("Tesla") print(car1) ``` ```shell Car class status Good from __str__ ``` --- ##### class diagram  --- ### 類別方法 (class method) :::info 類別中有 @classmethod 裝飾詞 (Decorator) 的方法，類別呼叫類別方法時，類別方法會傳入 cls 參數，指向類別 ::: ```python= class ClassName: # 類別方法(Class Method) @classmethod def class_metho(cls): ... ... ``` --- #### 車子類別 + 類別方法 ```python= class Car: status = "Good" # class attribute # 類別方法(Class Method) @classmethod def chk_status(cls): print("Car chk_staus is {cls.status}.") Car.chk_status() ``` ```shell Car chk_staus is Good. ```  --- ### 實例變數的存取方式 #### 車子的引擎號碼變數 ```python= class Car: def __init__(self, engin_no = "0000-0000"): self.engin_no = engin_no def __str__(self): return f"Car's engin_no is {self.engin_no}" car1 = Car("1234-5678") print(car1) car1.engin_no = "2468-1357" print(car1) ``` ```shell Car's engin_no is 1234-5678 Car's engin_no is 2468-1357 ``` :::danger 引擎號碼可以改 ！！！ ::: --- ##### class diagram  --- #### @property 實例變數的讀取控制 :::info @property 裝飾詞將方法轉換為只能讀取的變數 ::: ```python= class Car: def __init__(self, engin_no = "0000-0000"): self._engin_no = engin_no @property # engin_no just can be read def engin_no(self): return self._engin_no car1 = Car("1234-5678") print(f"car1.engin_no {car1.engin_no}") car1.engin_no = "2468-1357" ``` ```shell car1.engin_no 1234-5678 --------------------------------- AttributeError Traceback (most recent call last) <ipython-input-3-dd4183959b5d> in <module> 7 car1 = Car("1234-5678") 8 print(f"car1.engin_no {car1.engin_no}") ----> 9 car1.engin_no = "2468-1357" AttributeError: can't set attribute ``` --- #### @property 實例變數的修改 :::info @property 實例變數.setter ::: ```python= class Car: def __init__(self, engin_no = "0000-0000"): self._engin_no = engin_no @property # engin_no just can be read def engin_no(self): return self._engin_no @engin_no.setter def engin_no(self, engin_no): self._engin_no = engin_no car1 = Car("1234-5678") print(f"car1.engin_no {car1.engin_no}") car1.engin_no = "2468-1357" print(f"car1.engin_no {car1.engin_no}") ``` ```shell car1.engin_no 1234-5678 car1.engin_no 2468-1357 ``` --- ##### class diagram  --- ### 繼承 ( Inheritance ) :::info If you inherit money or property, you receive it from someone who has died. <font color=#FF0FF>繼承</font> If you inherit a characteristic or quality, you are born with it, because your parents or ancestors also had it. <font color=#FF6600>遺傳</font> ::: --- #### Pyhton 類別繼承 :::info 繼承可使類別擁有共同的屬性或方法，將共同的屬性或方法定義在父類別(Parent Class)中，而子類別(Child Class)則透過繼承得到共同的屬性或方法 ::: --- #### 兩種車子類別 ```python= class gasoline_Car: def __init__(self, brand, engin): self.brand = brand self.engin = engin class electric_Car: def __init__(self, brand, battery): self.brand = brand self.battery = battery gcar = gasoline_Car("Totyo", "Turbo") ecar = electric_Car("Tesla", "750kw") ``` :::danger brand 是一樣的屬性 ... ::: --- ###### class diagram  --- #### 車子類別 父類別 -- car :::info 車子共同的屬性 -- brand ::: ```python= class car: def __init__(self, brand): self.brand = brand car = car("Toyota") ```  --- #### 類別繼承 ```python= class child_class(parent_class): #super() is parent class ... ``` --- ###### gasoline_Car 繼承 car 類別 ```python= class car: def __init__(self, brand): self.brand = brand class gasoline_Car(car): def __init__(self, brand, engin): super().__init__(brand) self.engin = engin gcar = gasoline_Car("Totyo", "Turbo") ``` ---  --- #### 兩種車子繼承 car 類別 ```python= class car: def __init__(self, brand): self.brand = brand class gasoline_Car(car): def __init__(self, brand, engin): super().__init__(brand) self.engin = engin class electric_Car(car): def __init__(self, brand, battery): super().__init__(brand) self.battery = battery gcar = gasoline_Car("Totyo", "Turbo") ecar = electric_Car("Tesla", "750kw") ``` ---  --- #### 有兩個共同屬性 ```python= class car: def __init__(self, brand, engin_no): self.brand = brand self.engin_no = engin_no class gasoline_Car(car): def __init__(self, brand, engin_no, engin): super().__init__(brand, engin_no) self.engin = engin gcar = gasoline_Car("Totyo", "12345678", "Turbo") ``` ---  --- ### Operator overloading | Operator | Method | | :--------: | :--------: | | + | 'object.\_\_add\_\_(self, other) | |- |object.\_\_sub\_\_(self, other)| |* |object.\_\_mul\_\_(self, other)| |// |object.\_\_floordiv\_\_(self, other)| |/ |object.\_\_div\_\_(self, other)| |% |object.\_\_mod\_\_(self, other)| --- ###### \_\_add\_\_() example ```python= class MyTime: def __init__(self, h=0, m=0): self.hour = h self.min = m def __add__(self, other): nhour = self.hour+other.hour nmin = self.min+other.min if nmin >= 60: nhour = nhour + 1 nmin -= 60 if nhour >= 24: nhour -= 24 return MyTime(nhour, nmin) def __str__(self): return f"{self.hour:02} : {self.min:02}" time1 = MyTime(22, 40) time2 = MyTime(2, 30) time3 = time1 + time2 print(f"{time1} + {time2} = {time3}") ``` ```shell 22 : 40 + 02 : 30 = 01 : 10 ``` ---