作业：实现简单的shell sed替换功能和修改haproxy配置文件

1.实现简单的shell sed替换功能：

find_str='我有太多歌曲永远不会被唱起'
replace_str='YOUTAIDUODEGEQUYONGYUANBUHUIBEICHANGQI'

with open('yesterday','r',encoding='utf-8') as f,
    open('yesterday.bak','w',encoding='utf-8') as f_new:
    for line in f:  # f为一个迭代器，按行迭代
        if find_str in line:
            line = line.replace(find_str, replace_str)  # 字符串替换replace函数
        f_new.write(line)

2.修改haproxy配置文件(节点搜索、添加和删除)：

while True:

    menu=input('''
------请选择功能------
搜索节点请输入S:
添加节点请输入A:
删除节点请输入D:
退出请输入Q：
''',)

    if menu=='S':
        website=input('请输入网址：')
        node='backend'+' '+website
        with open('haproxy.txt','r',encoding='utf-8') as f:
            count=0
            N=-2
            for line in f:#使用迭代占用内存小
                if line.strip()==node:#去掉两边空格之后判断
                    N=count
                if count==N+1:
                    print('''节点{_website}信息为:{_info}
                    '''.format(_website=website,_info=line.strip()))
                count+=1
            if N==-2:
                print('该节点不存在')
            print(N)

    elif menu=='A':
        website=input('请输入您要添加的节点网址：')
        server=input('请输入您要添加的节点地址：')
        weight=input('请输入您要添加的节点weight：')
        maxconn=input('请输入您要添加的节点maxconn：')
        backend='backend'+' '+website
        record='        '+'server'+' '+server+' '+'weight'+' '+weight+' '+'maxconn'+' '+maxconn

        with open('haproxy.txt','a',encoding='utf-8') as f:
            f.write('
')
            f.write(backend)
            f.write('
')
            f.write(record)
            print('添加成功')

    elif menu=='D':

        website=input('请输入您要删除的节点网址：')
        backend='backend'+' '+website

        with open('haproxy.txt','r',encoding='utf-8') as f_read:
            readlines = f_read.readlines()
        with open('haproxy.txt','w',encoding='utf-8') as f_write:

            count=0
            N=-2
            for line in readlines:
                count+=1
                if line.strip()==backend:#删除网址
                    N=count
                    continue
                if count==N+1:#删除节点信息
                    print('已删除节点信息')
                    continue
                f_write.write(line)

            if N==-2:
                print('不存在该节点')
                for line in readlines:
                    f_write.write(line)
    elif menu=='Q':
        break
    else:
        print('输入不合法')