Python: Iterator Pattern

DuIterator.py

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# 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：

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# 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：

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Hello     Geovin Du     Goodbye     涂聚文