Python Telnet D-Link

import sys
import time
import telnetlib
from ipaddress import ip_network

f = open('switches.log', 'w')

HOSTS = list(ip_network('192.168.0.0/23').hosts())
# HOSTS = ['192.168.111.55', '192.168.111.104', '192.168.111.120']
LOGIN = 'USER'
PASSWORD = 'PASS'


def cmd(value):
    return value.encode('ascii') + b'\n'


def do(HOST, f):
    try:
        SUCCESS = False
        tn = telnetlib.Telnet(host=HOST, port=23, timeout=5)
        # tn.set_debuglevel(1)

        tn.expect([b'UserName:'], 2)
        tn.write(cmd(LOGIN))
        tn.expect([b'PassWord:'], 2)
        tn.write(cmd(PASSWORD))
        a, b, fail = tn.expect([b'Fail!:'], 2)
        if b'Fail' in fail:
            tn.expect([b'UserName:'], 2)
            tn.write(cmd(LOGIN))
            tn.expect([b'PassWord:'], 2)
            tn.write(cmd(PASSWORD))
            a, b, fail = tn.expect([b'Fail!:'], 2)
            if b'Fail' in fail:
                print(HOST + ' - Fail!')
                f.write(HOST + ' - Fail!\n')
                sys.exit(0)

        tn.write(cmd('enable admin'))
        tn.expect([b'PassWord:'], 2)
        tn.write(cmd('ADMINPASS'))

        tn.expect([b'admin#', b'4#', b'5#'], 5)
        tn.write(cmd('config igmp_snooping multicast_vlan_group_profile base add 1.2.3.4-5.6.7.8'))
        a, b, success = tn.expect([b'Success'], 5)
        if b'Success' in success:
            SUCCESS = True
            tn.write(cmd('show vlan vlanid 1'))
            tn.expect([b'admin#', b'4#', b'5#'], 5)
            tn.write(cmd('save all'))
            tn.expect([b'admin#', b'4#', b'5#'], 5)
            tn.write(cmd('logout'))
            print(HOST + ' - Success!')
            f.write(HOST + ' - Success!\n')
            return 0
        tn.write(cmd('config igmp_snooping multicast_vlan_group TV add 1.2.3.4-5.6.7.8'))
        a, b, success = tn.expect([b'Success'], 5)
        if b'Success' in success:
            SUCCESS = True
            tn.write(cmd('show vlan vlanid 1'))
            tn.expect([b'admin#', b'4#', b'5#'], 5)
            tn.write(cmd('save all'))
            tn.expect([b'admin#', b'4#', b'5#'], 5)
            tn.write(cmd('logout'))
            f.write(HOST + ' - Success!\n')
            print(HOST + ' - Success!')
            return 0
        if not SUCCESS:
            tn.expect([b'admin#', b'4#', b'5#'], 5)
            tn.write(cmd('logout'))
            print(HOST + ' - Fail!')
            f.write(HOST + ' - Fail!\n')
            return 0
    except:
        print(HOST + ' - Fail')
        f.write(HOST + ' - Fail!\n')


for HOST in HOSTS:
    do(str(HOST), f)
f.close()