一、读取文件，打印第三行时后面加入“徐亚平”
程序如下：
count=0
with open("test",mode="r",encoding="utf8") as f:
for line in f:
if count==2:
line="".join([line.strip(),"徐亚平"])
print(line.strip())
count+=1
1 Somehow, it seems the love I knew was always the most destructive kind 2 不知为何，我经历的爱情总是最具毁灭性的的那种 3 Yesterday when I was young 4 昨日当我年少轻狂 5 The taste of life was sweet 6 生命的滋味是甜的 7 As rain upon my tongue 8 就如舌尖上的雨露 9 I teased at life as if it were a foolish game 10 我戏弄生命 视其为愚蠢的游戏
二、修改文件，第三行时后面加入“徐亚平”
因为文件保存在相对应的内存块，故不能在文件前面和文件中间修改，只能在文件尾端追加。
故此时在第三行尾加入“徐亚平”，只能新建文件，删除原先的保留新建的满足题目要求。
程序如下：
count=0
with open("test2",encoding="utf8") as f_read,open("test3",mode="w",encoding="utf8") as f_write:
for line in f_read:
if count==2:
line="".join([line.strip(),"徐亚平\n"])
f_write.write(line)
count+=1
import os
os.rename("test2","test2_bak")
os.rename("test3","test2")
原文件test2
1 Somehow, it seems the love I knew was always the most destructive kind 2 不知为何，我经历的爱情总是最具毁灭性的的那种 3 Yesterday when I was young 4 昨日当我年少轻狂 5 The taste of life was sweet 6 生命的滋味是甜的 7 As rain upon my tongue 8 就如舌尖上的雨露 9 I teased at life as if it were a foolish game 10 我戏弄生命 视其为愚蠢的游戏
三、打印并显示进度条
import sys
for i in range(100):
s="\r%s%% %s"%(i+1,"#"*(i+1))
sys.stdout.write(s)
sys.stdout.flush()
import time
time.sleep(0.5)
print(s)
四、修改haproxy配置文件
1、查
输入：www.oldboy.org
获取当前backend下的所有记录
while True:
m = input("please input url:").strip()
flag = False
l = []
with open("haproxy.conf",encoding="utf8") as f_read: #打开文件并赋值为f_read
for line in f_read: #逐行读取文件haproxy.conf
if line.startswith("backend") and m in line: #如果是“backend”开头并且“m”在此行中
flag=True #不打印不需要，改变标志位值，中止本次操作，重新开始for循环
continue
if line.startswith("backend") and flag: #第二次读到“backend”开头所在的行，结束本层for全部循环
break
if flag: #读到“backend”开头并且“m”后面的行，追加此行到l列表中
l.append(line.strip())
for i in l: #逐条打印l列表中的数据
print(i)
1 global 2 log 127.0.0.1 local2 3 daemon 4 maxconn 256 5 log 127.0.0.1 local2 info 6 7 defaults 8 log global 9 mode http 10 timeout connect 5000ms 11 timeout client 50000ms 12 timeout server 50000ms 13 option dontlognull 14 15 listen stats :8888 16 stats enable 17 stats uri /admin 18 stats auth admin:1234 19 20 frontend oldboy.org 21 bind 0.0.0.0:80 22 option httplog 23 option httpclose 24 option forwardfor 25 log global 26 acl www hdr_reg(host) -i www.oldboy.org 27 use_backend www.oldboy.org if www 28 29 backend www.oldboy1.org 30 server 10.10.0.10 10.10.0.10 weight 9999 maxconn 33 31 server 10.10.10.1 10.10.10.1 weight 22 maxconn 2000 32 server 2.2.2.4 2.2.2.4 weight 20 maxconn 3000 33 34 backend www.oldboy2.org 35 server 3.3.3.3 3.3.3.3 weight 20 maxconn 3000 36 37 backend www.oldboy20.org 38 server 10.10.0.10 10.10.0.10 weight 9999 maxconn 33 39 40 41 data=input(): {"backend":"www.oldboy1.org","record":{server:...,weight:...,maxconn:...}}