输入网址，得到网址下的信息

网址文件py.txt内容：

global
       log 127.0.0.1 local2
       daemon
backend oldboy.org
       bind 0.0.0.0:80
       option httplog
       option httpclose
       option forwardfor
       log global
backend www.oldboy1.org
       server 10.10.0.10 10.10.0.10 weight 9999 maxconn 3333333
       server 10.10.10.1 10.10.10.1 weight 22 maxconn 2000
       server 2.2.2.4 2.2.2.4 weight 20 maxconn 3000
backend www.oldboy2.org
       server 3.3.3.3 3.3.3.3 weight 20 maxconn 3000
backend www.oldboy20.org
       server 10.10.0.10 10.10.0.10 weight 9999 maxconn 3333333

--------------------------------------------------

# 标志位
while 1:
    m=input("please input url:").strip()
    l=[]
    flag=False
    with open("py.txt",mode="r",encoding="utf8") as f_read:
        for line in f_read:
            if line.startswith("backend") and m in line:
                flag=True
                continue

            if line.startswith("backend") and flag:
                break

            if flag:
                l.append(line)

        for i in l:
            print(i)