def format_file_list(files):
        all_files_str = ""
        for i in range(len(files)):
                all_files_str +=  str(i)+":"+files[i]+"\n"
        return all_files_str

hosts_path = "C:\\Windows\\System32\\drivers\\etc"
files =  os.listdir(hosts_path)
os.chdir(hosts_path)

if os.getcwd() != hosts_path:
        print("Switch Dir to System32 Error,check permission!\npwd:"+os.getcwd())
        exit()

hosts_files = glob.glob("host*")
choosed_file_idx = int(input("Choose Hosts File Index:\n"+format_file_list(hosts_files)))
files_num = len(hosts_files)

if (choosed_file_idx < 0 or choosed_file_idx >= files_num) :
        print("Please choose a file in the lists!")
        exit()

print("Choosed idx:{0},file:{1}.".format(choosed_file_idx,hosts_files[choosed_file_idx]))
shutil.copy("hosts","hosts.bak")
shutil.copy(hosts_files[choosed_file_idx],"hosts")
print("Copy ok,then flush dns...")
os.system("ipconfig /flushdns")