LINUXホストのパスワードの一括変更とコマンドの送信

#!/usr/bin/python
import paramiko
import threading
def ssh2(ip,username,passwd,cmd):
    try:
        ssh = paramiko.SSHClient()
        ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())
        ssh.connect(ip,22,username,passwd,timeout=5)
        for m in cmd:
            stdin, stdout, stderr = ssh.exec_command(m)
            stdin.write("Y")
            out = stdout.readlines()
            for o in out:
                print o,
        print '%s\tOK
'%(ip)
        ssh.close()
    except :
        print '%s\tError
'%(ip)
if __name__=='__main__':
    cmd = ['/bin/echo "123456 | /usr/bin/passwd --stdin root"']
    username = "root"
    passwd = "okokok"
    threads = [5]
    print "Begin......"
    for i in range(230,236):
        ip = '192.168.1.'+str(i)
        a=threading.Thread(target=ssh2,args=(ip,username,passwd,cmd))
        a.start()