python - 双向链表迭代器python

Question

我正在构建一个双向链表，我正在努力在 PYTHON 中构建一个双向链表迭代器方法。

到目前为止，这是我的代码

class DoubleListNode:
    def __init__(self,data):
        self.data=data
        self.prev = None
        self.next= None

class ListIterator:
    def __init__(self):
        self._current = self.head

    def __iter__(self):
        return self

    def next(self):
        if self.size == 0 :
            raise StopIteration
        else:
            item = self._current.data
            self._current=self._current.next
            return item

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

    def add(self,data):
        newnode= DoubleListNode(data)
        self.size+=1
        if self.head is None:
            self.head = newnode
            self.tail = self.head
        elif data < self.head.data: # before head
            newnode.next = self.head
            self.head.prev= newnode
            self.head= newnode
        elif data > self.tail.data: # at the end
            newnode.prev= self.tail
            self.tail.next= newnode
            self.tail=newnode
        else:
            curNode = self.head
            while curNode is not None and curNode.data < data:
                curNode=curNode.next            
            newnode.next= curNode
            newnode.prev=curNode.prev
            curNode.prev.next= newnode
            curNode.prev=newnode

    def remove(self,data):
        curNode=self.head
        while curNode is not None and curNode.data!= data:
            curNode= curNode.next
        if curNode is not None:
            self.size -= 1
            if curNode is self.head:
                self.head= curNode.next
            else:
                curNode.prev.next=curNode.next
            if curNode is self.tail:
                self.tail=curNode.prev
            else:
                curNode.next.prev=curNode.prev

当我运行测试时，它说 TypeError: iteration over non-sequence。我做错了什么吗？

Answer 1

如发布的那样，代码未初始化(即 self.head 未定义)。

但总体而言，您的方向是正确的。看看the source for Python's collections.OrderedDict一个遍历双向链表的例子。

这是一个简化的例子:

class Link:
    def __init__(self, value, prev=None, next=None):
        self.value = value
        self.prev = prev
        self.next = next

    def __iter__(self):
        here = self
        while here:
            yield here.value
            here = here.next

    def __reversed__(self):
        here = self
        while here:
            yield here.value
            here = here.prev

if __name__ == '__main__':
    a = Link('raymond')
    b = Link('rachel', prev=a);  a.next=b
    c = Link('matthew', prev=b); b.next=c

    print 'Forwards:'
    for name in a:
        print name
    print
    print 'Backwards:'
    for name in reversed(c):
        print name