import getpass
import sys
import telnetlib
import time

host ="12.12.1.123"
user ="user_name"
passwd ="telnet_password"
tn = telnetlib.Telnet(host)
tn.read_until("login: ")
tn.write(user + "n")
tn.read_until("Password: ")
tn.write(passwd + "n")
time.sleep(5)
tn.write("lr n")
str_all=tn.read_until("$")
#f=open("/netperf/mntpt/array1/home/prg_use/op.txt", "w")
f=open("op.txt", "w")
f.write(str_all)
f.close()
tn.write("exit n")

print tn.read_all()

lr: not found
$