D =set( ["Tue","Wed","Thu","Fri","Sat"])

F =set( ["Mon","Tue","Wed"])

# Months = {"Jan", "Feb", "Mar"}

# dates={21,22,23}

D.add("Sun")

D.discard("Sun")

E = D|F

G = D&F

H = F - D

J = D >= F

# K =

print(J)

# print(Months)

# for i in D:

#    print(i)

二阶数组

centos7网卡报错,ip地址丢失不见等问题解决方法

问题出现:

ip地址丢失不见,网卡报错,当重启网卡时

Job for network.service failed because the control process exited with error code. See "systemctl status network.service" and "journalctl -xe" for details.

按照提示输入systemctl status network.service查看报错如下

Failed to start LSB: Bring up/down networking.

解决办法:

系统自带的NetworkManager这个管理套件出错，关掉.

关掉方法:

systemctl stop NetworkManager

systemctl disable NetworkManager

重新启动网络：

systemctl start network.service

class Node:

    def __init__(self,datavalue=None):

        self.datavalue = datavalue

        a = self.datavalue

        self.nextvalue = None

        b = self.nextvalue

class SLinkedList:

    def __init__(self):#链表程序先初始化，获取首地址

        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

            h = printval.nextvalue

list = SLinkedList()#实例化一个list，设首地址

list.headnode = Node("Mon")

e2 = Node("Tue")

e3 = Node("Wed")

list.headnode.nextvalue = e2

e2.nextvalue = e3

list.printvalue()

在链表的表首插入新节点的思路

实例化一个新节点，新节点的nextvalue指向现在链表的首节点的地址，新链表的首地址就是构造新的实例的地址

在链表的表末尾增加节点

实例化一个新的节点，现存的链表的最后一个节点的指针肯定是空，遍历现在的链表，找到指针为空的，将这个指针赋值为新的节点的地址