Unable to get login prompt via ssh using python script

enter code here

#!/usr/bin/python

import paramiko
import sys
import time
import Tkinter
import time, os, threading
from Tkinter import *
a=Tkinter.Tk()



#A function that logins and execute commands
def fn():
    HOST=raw_input('Enter HOST IP: ')

    USER=raw_input('Enter USER NAME: ')

    PASS=raw_input('Enter PASSWORD: ')

    client1=paramiko.SSHClient()
    client1.set_missing_host_key_policy(paramiko.AutoAddPolicy())
    client1.connect(HOST,username=USER,password=PASS)
    print "SSH connection to %s established" %HOST
    com="cat /etc/motd"
    print "Welcome to Account",
    com1=raw_input("Enter the command:")
    com2=raw_input("Enter if you you want to run multiple command:")
    #Gather commands and read the output from stdout
    stdin, stdout, stderr = client1.exec_command(com)
    print stdout.read()
    stdin, stdout, stderr = client1.exec_command( com1)
    print stdout.read()
    stdin, stdout, stderr = client1.exec_command( com2 )
    print stdout.read()
    client1.close()
    top = os.system("sudo su -")
    s = str(top)
    print "Logged out of device %s" %HOST



b = Button(a, text='Welcome to the Login World', command=fn)
b.pack()
b.mainloop()

Output are below::

[root@xyz ~]#
Enter HOST IP: 10.12.132.143
Enter USER NAME: abc
Enter PASSWORD:*************
SSH connection to 10.129.136.150 established
Welcome to  Account Enter the command:uptime;uname -a
Enter if you you want to run multiple command:

01:02:48 up 4 days, 15:28,  3 users,  load average: 1.02, 1.01, 1.00
Linux   10.12.132.143 2.6.32-642.6.2.el6.x86_64 #1 SMP Mon Oct 24 10:22:33 EDT 2016 x86_64 x86_64 x86_64 GNU/Linux
[root@xyz ~]#   -->this is the error it should login to  10.12.132.143 server but it is login to my master server
[root@xyz ~]#.