python 類相關概念理解

class CLanguage :
    # 下面定義瞭2個類變量
    name = "python語言"
    add = "http://c.biancheng.net.python"
    # __init__是構造方法，也屬於實例方法  
    def __init__(self,name,add):
        #下面定義 2 個實例變量
        self.name = name
        self.add = add
        print(name,"網址為：",add)
    # 下面定義瞭一個say實例方法
    def say(self, content):
        print(content)
    #下面定義瞭一個count實例方法   
    def count(self,money):
    #下面定義瞭一個局部變量sale
        sale = 0.8*money
        print("優惠後的價格為：",sale)
    #下面定義瞭一個類方法
    @classmethod
    def info(cls):
        print("正在調用類方法",cls)
    #下面定義瞭一個靜態方法
    @staticmethod
    def info(name,add):
        print(name,add)
# 將該CLanguage對象賦給clanguage變量
# 通過類名直接調用實例方法
# CLanguage.say("通過類名直接調用實例方法")會報錯，必須手動將 clang 這個類對象傳給self 參數
clang = CLanguage("C語言中文網1","http://c.biancheng.net")#傳入的參數要和init的一樣
CLanguage.say(clang, "通過類名直接調用實例方法")
# 通過類對象直接調用實例方法
clang2 = CLanguage("C語言中文網2","http://c.biancheng.net")
clang2.say("通過類對象直接調用實例方法")

#輸出
C語言中文網1 網址為： http://c.biancheng.net
通過類名直接調用實例方法
C語言中文網2 網址為： http://c.biancheng.net
通過類對象直接調用實例方法

class Person(object):
    def __init__(self,name,sex):
        self.name = name
        self.sex = sex
    def print_title(self):
        if self.sex == "male":
            print("man")
        elif self.sex == "female":
            print("woman")
class Child(Person):                            # Child 繼承 Person
    pass
May = Child("May","female")
Peter = Person("Peter","male")
print(May.name,May.sex,Peter.name,Peter.sex)    # 子類繼承父類方法及屬性
May.print_title()
Peter.print_title()

#輸出
May female Peter male
woman
man

class Person(object):
    pass
class Child(Person):                 # Child 繼承 Person
    pass
May = Child()
Peter = Person()    
print(isinstance(May,Child))         # True
print(isinstance(May,Person))        # True
print(isinstance(Peter,Child))       # False
print(isinstance(Peter,Person))      # True
print(issubclass(Child,Person))      # True

class Person(object):
    def __init__(self,name,sex):
        self.name = name
        self.sex = sex
    def print_title(self):
        if self.sex == "male":
            print("man")
        elif self.sex == "female":
            print("woman")
class Child(Person):                # Child 繼承 Person
    def print_title(self):
        if self.sex == "male":
            print("boy")
        elif self.sex == "female":
            print("girl")
May = Child("May","female")
Peter = Person("Peter","male")
print(May.name,May.sex,Peter.name,Peter.sex)
May.print_title()
Peter.print_title()

對擴展開放（Open for extension）：允許子類重寫方法函數
對修改封閉（Closed for modification）：不重寫，直接繼承父類方法函數

class Person(object):
    def __init__(self,name,sex):
        self.name = name
        self.sex = sex
class Child(Person):                          # Child 繼承 Person
    def __init__(self,name,sex,mother,father):
        Person.__init__(self,name,sex)        # 子類對父類的構造方法的調用
        self.mother = mother
        self.father = father
May = Child("May","female","April","June")
print(May.name,May.sex,May.mother,May.father)   

class Person(object):
    def __init__(self,name,sex):
        self.name = name
        self.sex = sex
    def print_title(self):
        if self.sex == "male":
            print("man")
        elif self.sex == "female":
            print("woman")
class Child(Person):
    pass
class Baby(Child):
    pass
May = Baby("May","female")        # 繼承上上層父類的屬性
print(May.name,May.sex)         # May female
May.print_title()                 #woman 可使用上上層父類的方法

class Child(Person):
    def print_title(self):
        if self.sex == "male":
            print("boy")
        elif self.sex == "female":
            print("girl")
class Baby(Child):
    pass
May = Baby("May","female")
May.print_title()                # girl 優先使用上層類的方法

# 字符串，列表，元祖，字典，集合等等，都是可迭代對象
for i in [1, 2, 3]:
    print(i)
obj = {"a": 123, "b": 456}
for k in obj:
    print(k)

class foo(object):
	def __iter__(self):
		return 迭代器對象(生成器對象)
obj = foo() #obj是可迭代對象

#創建迭代器
class IT(object):
	def __init__(self):
		self.counter = 0
	def __iter__(self):
		return self
	def __next__(self):
		self.counter += 1
		if self.counter == 3:
			raise StopIteration()
#創建可迭代器對象
class foo(object):
	def __iter__(self):
		return IT()
obj = foo() #obj是可迭代對象
for item in obj:   #循環可迭代對象時,內部先執行obj.__iter__()並獲取迭代器對象,然後再不斷的執行迭代器對象的__next__方法
	print(item)

# 方法1: iter()將可迭代對象轉換為迭代器
list=[1, 2, 3, 4]
it = iter(list)    # 創建迭代器對象
#使用next()遍歷數據
print (next(it))  #1
print (next(it))  #2
#使用for循環遍歷數據,for循環由於簡潔,更常用
#for循環會執行迭代器的iter並獲得返回的對象,一直反復的去執行next(對象)
for x in it:
    print (x, end=" ")   # 3 4
print (next(it))   #StopIteration
# 方法2: 創建一個迭代器
class MyNumbers:
  def __iter__(self):
    self.a = 1
    return self
  def __next__(self):
    if self.a <= 20:
      x = self.a
      self.a += 1
      return x
    else:
      raise StopIteration
#通過iter()和next()訪問 
myclass = MyNumbers()
myiter = iter(myclass)
print(next(myiter))
print(next(myiter))
print(next(myiter))
for x in myiter:
  print(x)
print(next(myiter))

#創建瞭一個 num 生成器對象。顯然，和普通函數不同，intNum() 函數的返回值用的是 yield 關鍵字，而不是 return 關鍵字，此類函數又成為生成器函數。
#創建生成器函數
def intNum():
    print("開始執行")
    for i in range(5):
        yield i
        print("繼續執行")
#創建生成器對象num
num = intNum()
#調用 next() 內置函數
print(next(num))  #0
#調用 __next__() 方法
print(num.__next__())  #1
#通過for循環遍歷生成器
for i in num:  #2 , 3, 4
    print(i)

num = intNum()
print(list(num))
num = intNum()
print(tuple(num)