Python: Iterator Pattern

DuIterator.py

# 迭代器模式 Iterator Pattern

# Doubly Linked List
class Node(object):
    def __init__(self, value, nextNode, prevNode):
        self.value = value
        self.next = nextNode
        self.prev = prevNode


class DoublyLinkedList(object):
    def __init__(self):
        self.size = 0
        self.head = None
        self.tail = None

    def isEmpty(self):
        return self.head is None

    def addLast(self, value):
        if self.isEmpty():
            tmp = Node(value, None, None)
            self.head = tmp
            self.tail = tmp
            self.size += 1
            return

        self.tail.next = Node(value, None, self.tail)
        self.tail = self.tail.next
        self.size += 1

    def getIterator(self):
        return DLinkIterator(self.head)

    def getReverseIterator(self):
        return DLinkReverseIterator(self.tail)

# Forward Iterator:
class DLinkIterator(object):
   def __init__(self, startNode):
       self.current = startNode

   def hasNext(self):
       return self.current != None

   def next(self):
       if not self.hasNext():
           raise IndexError
       val = self.current.value
       self.current = self.current.next
       return val
# Reverse Iterator:
class DLinkReverseIterator(object):
   def __init__(self, startNode):
       self.current = startNode

   def hasNext(self):
       return self.current != None

   def next(self):
       if not self.hasNext():
           raise IndexError
       val = self.current.value
       self.current = self.current.prev
       return val

　　

main.py 调用：

# 迭代器模式 Iterator Pattern
myList = DuIterator.DoublyLinkedList()

myList.addLast("Hello")
myList.addLast("Geovin Du")
myList.addLast("Goodbye")
myList.addLast("涂聚文")

# Iterate the list forwards:
forwardIter = myList.getIterator()

while forwardIter.hasNext():
 print(forwardIter.next())
 print("\n")

　　

输出：

Hello


Geovin Du


Goodbye


涂聚文