python物件導向（下）

物件導向第三講

• python父類如果實現了構造方法，子類沒有，例項化子類物件時會預設呼叫父類的構造方法

  class G():
      def __init__(self):
          print('G __init__ invoke...')
  class P():
      def __init__(self):
          print('P __init__ invoke...')
  class A(P,G):
      pass
      #def __init__(self):
      #    P.__init__(self)
      #print('A __init__ invoke...')
  if __name__ == '__main__':
      a=A()

• 父類方法呼叫多種方法

  class P1():
      def __init__(self):
          print('P1 __init__ invoke...')
  class P2():
      def __init__(self):
          print('P2 __init__ invoke...')
  class A(P1,P2):
      def __init__(self):
          P1.__init__(self)
          P2.__init__(self)
          print('A __init__ invoke...')
  
  if __name__ == '__main__':
      a=A()

• 第二種方法super(A.self)

  class G():
      def __init__(self):
          print('G __init__ invoke...')
  class P():
      def __init__(self):
          print('P __init__ invoke...')
  class A(P,G):
      def __init__(self):
          #P.__init__(self)
          #G.__init__(self)
          super(A,self).__init__()
          print('A __init__ invoke...')
  if __name__ == '__main__':
      a=A()

• 靜態方法無法訪問物件的自身屬性變數

  class A():
      method=1#靜態屬性
      def __init__(self,name):
          self.name=name
      def run(self):
          print('run invoke...')
      @staticmethod
      def func(x):
          print('self.name=%s'%x)
          print('func invoke...')
      @classmethod
      def test(cls):
          print('test...')
  if __name__ == '__main__':
      a=A('name')
      a.run()
      A.func('ZangzzzZ')
      A('xxx').func('yyy')
      A.test()
      print(dir(A.run('name')))
      print(dir(A))
      A.func('ZangzzzzZ')

• 方法過載 str

  class A(object):
      def __init__(self,name,age):
          self.name=name
          self.age=age
      def __str__(self):#方法過載
          return 'name=%s,age=%d'%(self.name,self.age)
  if __name__ == '__main__':
      a=A('ZangzzZ',20)
      print(str(a))#str(a)和a

• 單連結串列結構

  #實現一個單連結串列
  
  #用node來作為連結串列的節點抽象類
  class Node():
  
      def __init__(self,data):
          self.data=data
          self.next=None
      def show(self):
          print('node data=%d'%self.data)
      def __str__(self):
          return 'node data=%s'%self.data
  class LinkList():
      def __init__(self):
          self.head=None
      def insertFirst(self,data):
          newNode = Node(data)#建立新節點
          newNode.next=self.head
          self.head = newNode
      def deleteFirst(self):
          tmpNode= self.head
          self.head=self.head.next
          return tmpNode
      def travel(self):
          currentNode = self.head
          while currentNode is not None:
              print(currentNode)
              currentNode = currentNode.next
  if __name__ == '__main__':
      n1=Node('A')
      n2=Node('B')
      n3=Node('C')
      link=LinkList()
      link.insertFirst(n1)
      link.insertFirst(n2)
      link.insertFirst(n3)
      link.travel()
      print('+'*30)
      link.deleteFirst()
      link.deleteFirst()
      link.deleteFirst()
      link.travel()

• 過載__iter__和__next__實現一個可迭代的型別(有限迴圈的版本)

  import random
  class A():
      def __init__(self,seq):
          '''seq type(iterable)'''
          self.seq=seq
          self.index=0
      def __iter__(self):
          return self#返回當前物件
      def __next__(self):
          if self.index > len(self.seq) - 1:
              raise StopIteration
          else:
              tmp = self.seq[self.index]
              self.index+=1
              return tmp
  if __name__ == '__main__':
      a=A([1,2,3,50,43])
      for item in a:
          print(item)

• 過載__iter__和__next__實現一個可迭代的型別(無限迴圈的版本)

  import random
  class A():
      def __init__(self,seq):
          '''seq type(iterable)'''
          self.seq=seq
      def __iter__(self):
          return self#返回當前物件
      def __next__(self):
          return self.seq[random.randint(0,len(self.seq)-1)]
  if __name__ == '__main__':
      a=A([1,2,3])
  
      for item in a:
          print(item)