從子類的用戶隱藏超類方法

Question

我想知道是否有可能阻止用戶在使用子類時調用父類的方法。同時，我希望這些方法可以用於孩子班級的方法。

例如，假設我有一個鏈接列表的實現。然後，我通過繼承（不知道它是否是好的設計...）來爲它構建一個ADT堆棧實現。因此，我希望從Stack類的用戶中「隱藏」LinkedList類的方法。

的LinkedList：

class LinkedList(object): 
    class Node(object): 
     """ 
     Inner class of LinkedList. Contains a blueprint for a node of the LinkedList 
     """ 
     def __init__(self, v, n=None): 
      """ 
      Initializes a List node with payload v and link n 
      """ 
      self.value=v 
      self.next=n 

    def __init__(self): 
     """ 
     Initializes a LinkedList and sets list head to None 
     """ 
     self.head=None 

    def insert(self, v): 
     """ 
     Adds an item with payload v to beginning of the list 
     in O(1) time 
     """ 
     Node = self.Node(v, self.head) 
     self.head = Node 
     print("Added item: ", Node.value, "self.head: ", self.head.value) 

    def size(self): 
     """ 
     Returns the current size of the list. O(n), linear time 
     """ 
     current = self.head 
     count = 0 
     while current: 
      count += 1 
      current = current.next 
     return count 

    def search(self, v): 
     """ 
     Searches the list for a node with payload v. Returns the node object or None if not found. Time complexity is O(n) in worst case. 
     """ 
     current = self.head 
     found = False 
     while current and not found: 
      if current.value == v: 
       found = True 
      else: 
       current = current.next 
     if not current: 
      return None 
     return current 

    def delete(self, v): 
     """ 
     Searches the list for a node with payload v. Returns the node object or None if not found. Time complexity is O(n) in worst case. 
     """ 
     current = self.head 
     previous = None 
     found = False 
     while current and not found: 
      if current.value == v: 
       found = True 
      else: 
       previous = current 
       current = current.next 
     # nothing found, return None 
     if not current: 
      return None 
     # the case where first item is being deleted 
     if not previous: 
      self.head = current.next 
     # item from inside of the list is being deleted  
     else: 
      previous.next = current.next 

     return current 

    def __str__(self): 
     """ 
     Prints the current list in the form of a Python list    
     """ 
     current = self.head 
     toPrint = [] 
     while current != None: 
      toPrint.append(current.value) 
      current = current.next 
     return str(toPrint) 

堆棧：

from PythonADT.lists import LinkedList 

class Stack(LinkedList): 
    def __init__(self): 
     LinkedList.__init__(self) 

Answer 1

下面是一類申報保護的正式語法和私有方法。

1. 在父類中聲明的受保護的方法可以從子類調用。
2. 在父類中聲明的私有方法將從子類隱藏。

凸起例外是：

# AttributeError: '<ChildClass>' object has no attribute '__<private_function>'

步驟1 - 聲明在class Parent私人和保護方法。

class Parent(object): 
    # a private method starts by 2 '_' 
    def __parent_private(self): 
     print('inside __parent_private()') 

    # a protected method starts by 1 '_' 
    def _parent_protected(self): 
     print('inside _parent_protected()') 

步驟2 - 聲明函數調用從class Child兩個功能。

class Child(Parent): 

    def call__parent_private(self): 
     self.__parent_private() 

    def call_parent_protected(self): 
     self._parent_protected() 

步驟3 - 創建class Child一個實例來檢查private和protected的訪問。

myChild = Child() 

Check of protected method from the Child class ==> Access is allowed

# internal access of protected method 
myChild.call_parent_protected() 

輸出： 「inside _parent_protected()」

# direct access of protected method 
myChild._parent_protected() 

輸出： 「inside _parent_protected()」

Check of private method from the Child class ==> Access is denied

# internal access of private method 
myChild.call__parent_private() 

錯誤： 「AttributeError: 'Child' object has no attribute '_Child__parent_private'」

# direct access of private method 
myChild.__parent_private() 

錯誤： 「AttributeError: 'Child' object has no attribute '__parent_private'」