python修改haproxy

def select(arg):
    result = []
    flag = False                                            #设置标记点
    with open("haproxy.txt", "r+", encoding="utf-8") as f:
        for line in f:                                      #逐行读文件
            if line.strip() == "backend %s" % arg:
                flag = True
                continue
            if line.strip().startswith("backend"):
                flag = False
            if flag:
                result.append(line)
    return result

def add():
    inf_tmp = input("""input info: """)
    inf = eval(inf_tmp)
    if select(inf['backend']):                                              #判断是否存在
        return print(("the url exist"))
    else:
        with open("haproxy.txt", "r+", encoding="utf-8") as f:
            for line in f:
                f.write("\nbackend {url}\n".format(url = inf['backend']))
                f.write("\t\tserver {red1}  weight {num1}  maxconn {num2}\n".format(red1 = inf['record']['server'],
                num1 = inf['record']['weight'],
                num2 = inf['record']['maxconn']))
                return print("Adding record successfully.")

def remove():
    del_inf = eval(input("delete info: "))
    if select(del_inf['backend']):                                          #判断是否存在
        with open("haproxy.txt", "r+", encoding='utf-8') as file:
            file_tmp = open("haproxy_tmp.txt", 'w')
            line_ful = "backend {website}\n".format(website=del_inf['backend'])
            for line in file:
                if 'backend' not in line:
                    file_tmp.write(line)
                elif line != line_ful:
                    file_tmp.write(line)
                else:
                    print('Delete {line} \t\t{content}\n'.format(line=line, content=file.readline().strip()))
            file_tmp.close()
            file_tmp = open("haproxy_tmp.txt", 'r')
            with open("haproxy.txt", "w", encoding='utf-8') as file:
                for line in file_tmp:
                    file.write(line)
            file_tmp.close()
            return print("delect successfully")
    else:
        return print("error!")

def sel():
    url = input("url: ")
    ret = select(url)
    for i in ret:
        print(i)

while True:
    choice = input("select, add, delete, quit: ")
    if choice == "select":
        sel()
    elif choice == "add":
        add()
    elif choice == "delete":
        remove()
    elif choice == "quit":
        break

 

ps:有个小问题，删除的时候不能把空行删除，请大神指教

需要建两个文件：“haproxy.txt","haproxy_tmp.txt"