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OOP

Posted on Edited on In Disqus:
Symbols count in article: 2.7k Reading time ≈ 2 mins.

介紹

物件導向程式設計(Object-oriented programming，簡稱OOP)，它是一個具有物件(Object)概念的開發方式，能夠提高軟體的重用性、擴充性及維護性。

物件中包含

  • 類別(Class)
  • 物件(Object)
  • 屬性(Attribute)
  • 建構式(Constructor)
  • 方法(Method)

Creating Class and Object

建立classclassname :

建立物件obj = class()

Python 函式isinstance()來判斷類別(Class)與物件(Object)的關係。

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class animal:

    # class attribute
    species = "bird"

    # instance attribute
    # 初始化
    def __init__(self, name, age):
        self.name = name #名稱屬性
        self.age = age   #年齡屬性


# obj = class()

# instantiate the animal class
blu = animal("Blu", 10)
woo = animal("Woo", 15)

# access the class attributes
print(f"Blu is a {blu.__class__.species}")
print(f"Woo is also a {woo.__class__.species}")

# __class__.species. 類的所有實例的類屬性都相同

# access the instance attributes
print(f"{blu.name} is {blu.age} years old")
print(f"{woo.name} is {woo.age} years old")

# isinstance
print(isinstance(blu, animal))  # 執行結果：True

ps：blu.__class__.species取的class 建立attribute。

  • 結果如下 :

Blu is a bird
Woo is also a bird
Blu is 10 years old
Woo is 15 years old
True

方法(Method)

定義方法(Method)和函式(Function)的語法很像，都是 def 關鍵字開頭，接著自訂名稱。

至少要有一個self參數。

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class animal:

    # instance attributes
    def __init__(self, name, age):
        self.name = name
        self.age = age

    # instance method
    def sing(self, song):
        return f"{self.name} sings {song}"

    def dance(self):
        return f"{self.name} is now dancing"


# instantiate the object
blu = animal("Blu", 10)

# call our instance methods
print(blu.sing("'Happy'"))
print(blu.dance())

  • 結果如下 :

Blu sings ‘Happy’
Blu is now dancing

Inheritance

繼承是一種創建新類以使用現有類的細節而不修改它的方法。

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class dogfather:

    def __init__(self):
        print("dogfather is ready")

    def whoisThis(self):
        print("dogfather")

    def swim(self):
        print("dogfather faster")

# child class


class dog(dogfather):

    def __init__(self):

        # call super() function
        # 繼承
        super().__init__()
        print("dog is ready")

    def whoisThis(self):
        print("dog")

    def run(self):
        print("Run faster")


p1 = dog()
p1.whoisThis()
p1.swim()#繼承父方法才可呼叫
p1.run()

ps：super()在__init__()方法中使用了函數。
這允許我們__init__()在子類中運行父類的方法。

  • 結果如下 :

dogfather is ready
dog is ready
dog
dogfather faster
Run faster

Encapsulation(private)

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class Price:

    def __init__(self):
        # private obj
        self.__maxprice = 900

    def sell(self):
        print(f"Selling Price: {self.__maxprice}")

    def setMaxPrice(self, price):
        self.__maxprice = price


c = Price()
c.sell()

# change the price
c.__maxprice = 1000
c.sell()

# using setter function
c.setMaxPrice(1000)
c.sell()



ps：private 物件 無法直接修改數值。

  • 結果如下 :

Selling Price: 900
Selling Price: 900
Selling Price: 1000

參考網站

Parewa Labs Pvt
Mike Ku

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