双向链表的特点是：第一个元素的 prev 是None
1 # 双向链表： 2 class Node: 3 def __init__(self, node=None, prev=None, next=None): 4 # 注意顺序，因为实例化，一般不会关键字传参， 如果node= None(1) 1 是给node形参的，如果形参列表不同，则会出现异常 5 self.prev = prev 6 self.node = node 7 self.next = next 8 9 def __repr__(self): 10 return '{} <-- {} --> {}'.format( 11 self.prev.node if self.prev else None, 12 self.node, 13 None if self.next is None else self.next.node) 14 15 class DoubleLinkList: 16 def __init__(self, head= None, tail=None): 17 self.head = head 18 self.tail = tail 19 self.lens = 0 20 21 def append(self, node): 22 node = Node(node) 23 if self.head is None: 24 self.head = node 25 else: 26 self.tail.next = node 27 node.prev = self.tail 28 self.tail = node 29 self.lens += 1 30 31 def iternode(self, reverse=True): 32 if self.head is None: 33 raise Exception('This is a Emppty linklist') 34 current = self.head if reverse else self.tail 35 while current: 36 yield current 37 current = current.next if reverse else current.prev 38 39 def __iter__(self): 40 if self.head is None: 41 raise Exception('This is a Emppty linklist') 42 current = self.head 43 while current: 44 yield current 45 current = current.next 46 47 def __getitem__(self, index): 48 reverse = True if index>=0 else False 49 start = 0 if index>=0 else 1 50 for i, v in enumerate(ll.iternode(reverse), start): 51 if i == abs(index): 52 return v 53 54 def __setitem__(self, index, value): 55 ll[index].node = value 56 57 def __len__(self): 58 return self.len 59 60 def remove(self): 61 pass 62 # 先判断是否为空 63 # 需要遍历，利用iter 64 # 注意是中间，第一个，还是尾部删除 65 66 def pop(self): 67 pass 68 # 值删除尾部，self.tail.next = None 69 70 def insert(self, index): 71 pass 72 # 类似于remove 73 74 75 76 ll = DoubleLinkList() 77 ll.append(1) 78 ll.append(2) 79 ll.append(3) 80 ll.append(4) 81 ll.append(5) 82 83 for i in ll.iternode(False): 84 print(i) 85 print('----'* 20) 86 print(ll[-1]) 87 88 ll[-1] = 10000 89 print(ll[-1])
部分打印结果：
