LAN Host Discovery Script [Python]

#!/usr/bin/env python

__license__ = 'GPL-3'
__version__ = '0.1'
__author__  = 'irenicus09'
__date__    = '18/05/2012'

"""
This simple script relies on Nmap to discover hosts on LAN,
finds hosts using the Ping scan technique, parses & presents data
in a clear, readable format for commandline users.

Note: Edit the value of IP Range as required.
"""

import subprocess, os
from clint.textui import colored

# Edit the following values as required
ipRange = '192.168.0.1/24'
fileName = 'Hosts.txt'

# Don't edit this, list for storing result
hostList = []

def FindHosts():
    if ((os.path.exists(fileName)) == False):
        cmd = subprocess.Popen("nmap -sP %s | grep -o -P '(\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})' >> %s" % (ipRange, fileName), shell=True, stdin=subprocess.PIPE, stdout=subprocess.PIPE)
        cmd.communicate()
    else:
        os.remove(fileName)
        FindHosts()

def PrintHosts():
    try:
        fileObject = open(fileName, 'r+')
        hostList   = fileObject.readlines()
        fileObject.close()

        count = 0

        print colored.green('=')*50
        length = '\t\t%d HOSTS FOUND' % len(hostList)
        print colored.cyan(length)
        print colored.green('=')*50

        for i in hostList:
            count += 1
            value = '%s)'.ljust(4) % count
            i = '%s'.ljust(15) % (i.strip())
            print colored.green(value) + colored.red(i)
    except (Exception):
        print '\n[!] Error opening file %s' % fileName


if __name__ == '__main__':
    FindHosts()
    PrintHosts()