python telnet and put the message in a particular log file

Question

hi I am coding the python script to login telnet and it has to write log file to op.txt

the absolute path is

/netperf/mntpt/array1/home/prg_use/op.txt

the python code

ptlog.py

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")
tn.write("touch op.txt \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()

the server side in terminal is

$

 lr: not found
$

however, I wanna it wrote

lr: not found

in

op.txt

but it did not happen, can any one tell me how to do it, thank you

if I code

f=open("/netperf/mntpt/array1/home/prg_use/op.txt", "w")

it will show

no such file or directory '/netperf/mntpt/array1/home/prg_use/op.txt'

I think it is not the path problem, I can touch op.txt

, its

str_all=tn.read_until("$")

can not copy the return message and then write in op.txt