class Node:

def __init__(self,datavalue=None):

self.datavalue = datavalue

a =self.datavalue

self.nextvalue =None

? ? ? ? b =self.nextvalue

class SLinkedList:

def __init__(self):#鏈表程序先初始化，獲取首地址

? ? ? ? self.headnode =None

? ? ? ? c =self.headnode

def printvalue(self):

printval =self.headnode

d = printval

while printval:

f = printval

print(printval.datavalue)

e = printval.datavalue

printval = printval.nextvalue

def atbegin(self,newdata):

newnode = Node(newdata)

newnode.nextvalue =self.headnode

self.headnode = newnode

def atlast(self,newdata):

newnode= Node(newdata)

nextnode =self.headnode

while(nextnode.nextvalue):

nextnode = nextnode.nextvalue

nextnode.nextvalue = newnode

def atmid(self,mid,newdata):

newnode = Node(newdata)

newnode.nextvalue = mid.nextvalue#有先后順序，先給值，再給地址

? ? ? ? mid.nextvalue = newnode

list = SLinkedList()#實例化一個list，設首地址

list.headnode = Node("Mon")##返回的是一個指針

x = Node("Mon")

e2 = Node("Tue")

y = Node("Tue")

e3 = Node("Wed")

list.headnode.nextvalue = e2

e2.nextvalue = e3

# list.atbegin("sun")

# list.atlast("sun")

list.atmid(e2,"Fri")

list.printvalue()