#构造一个节点的类  1 class Node(object):  2     def __init__(self, value=None):
  3         self.value = value
  4         self.next = None
  5
  6 class LinkedList(object):
  7
  8     def __init__(self, root=None, maxsize=None):#留一个尾节点是为了方便插入元素这样能实现O(1)时间的插入操作
  9         self.tailnode = None
 10         self.root = Node()
 11         self.count = 0#可以自己设定Linked List最大能存多少元素
 12         self.maxsize = maxsize
 13
 14     def __len__(self):
 15         return self.count
 16
 17     def append(self, value):
 18         node = Node(value)　　　　　　　　#插入第一个值时
 19         if self.tailnode is None:
 20             self.root.next = node
 21         else:
 22             if self.maxsize and len(self) >= self.maxsize:
 23                 raise Exception('LinkedList is Full')
 24             self.tailnode.next = node
 25         self.tailnode = node
 26         self.count += 1
 27
 28     def appendleft(self, value):
 29         if self.maxsize and len(self) >= self.maxsize:
 30             raise Exception('LinedList Full')
 31         node = Node(value)　　　　　　　　#可能在插入之前这个单链表是空的因此要处理self.root和self.tailnode
 32         if self.tailnode is None:
 33             self.root.next = node
 34             self.tailnode = node
 35         else:
 36             headnode = self.root.next
 37             self.root.next = node
 38             node.next = headnode
 39         self.count += 1
 40
 41     def __iter__(self):
 42         for node in self.iter_node():
 43             yield node.value
 44
 45     def iter_node(self):
 46         headnode = self.root.next
 47         while headnode:
 48             yield headnode
 49             headnode = headnode.next
 50
 51     def remove(self, value):
 52         prevnode = self.root
 53         for node in self.iter_node():
 54             if node.value == value:
 55                 prevnode.next = node.next
 56                 self.count -= 1
 57                 if node is self.tailnode:
 58                     self.tailnode = prevnode
 59                 del node
 60                 return 1
 61             prevnode = node
 62         return -1
 63
 64     def find(self, value):
 65         for index, node in enumerate(self.iter_node()):
 66             if node.value == value:
 67                 return index
 68         return -1
 69
 70     def popleft(self):
 71         if self.tailnode is None:
 72             raise Exception("pop from empty LinkedList")
 73         headnode = self.root.next
 74         value = headnode.value
 75         if headnode is self.tailnode:
 76             self.tailnode = None
 77         else:
 78             self.root.next = headnode.next
 79         del headnode
 80         self.count -= 1
 81         return value
 82
 83     def clear(self):
 84         for node in self.iter_node():
 85             del node
 86         self.root = Node()
 87         self.tailnode = None
 88         self.count = 0
 89
 90     def reverse(self):
 91         prevnode = self.root.next
 92         self.tailnode = prevnode
 93         curnode = prevnode.next
 94         prevnode.next = None
 95         while curnode:
 96             nextnode = curnode.next
 97             curnode.next = prevnode
 98             if nextnode is None:
 99                 self.root.next = curnode
100             prevnode = curnode
101             curnode = nextnode
102 if __name__ == "__main__":
103     l = LinkedList()
104     l.append(1)
105     l.append(2)
106     l.append(3)
107     assert len(l) == 3
108     assert list(l) == [1, 2, 3]
109     l.appendleft(0)
110     assert list(l) == [0, 1, 2, 3]
111     assert len(l) == 4
112     l.remove(2)
113     assert list(l) == [0, 1, 3]
114     assert l.popleft() == 0
115     l.append('a')
116     l.append('b')
117     l.reverse()
118     assert list(l) == ['b', 'a', 3, 1]
119     l.clear()
120     assert len(l) == 0
121     assert list(l) == []