Update/delete entries in system hosts file by a hosts file or URL

updateHost.py

#!/usr/bin/env python2.7

import re
import os, os.path
import sys
import urllib2
from contextlib import closing

USAGE = "{0} hosts".format(sys.argv[0])

class Hosts(object):
	ipmatch = re.compile(r'^(25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9][0-9]|[1-9])(\.(25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9][0-9]|[0-9])){3}$')
	if sys.platform == 'win32':
		hostsLocation = \
				os.sep.join((os.environ['windir'], r'system32\drivers\etc\hosts'))
	else:
		hostsLocation = '/etc/hosts'

	def __init__(self):
		self.hosts, self.unkownLines = \
				self.parseHosts(self.hostsLocation)

	def update(self, hostsfile):
		newhosts, _ = self.parseHosts(hostsfile)
		self.hosts.update(newhosts)

	def parseHosts(self, hostsfile):
		hosts = {}
		unkownLines = []
		if not os.path.exists(hostsfile):
			if hostsfile.startswith('http'):
				gopen = urllib2.urlopen
			else:
				return hosts, unkownLines
		else:
			gopen = open
		with closing(gopen(hostsfile)) as f:
			for l in f:
				l = l.strip()
				if not l or l.startswith('#'):
					continue
				ip, domain = l.split()[:2]
				if self.ipmatch.search(ip):
					hosts[domain] = ip
				else:
					unkownLines.append(l)
		return hosts, unkownLines

	def writeHosts(self):
		if os.path.exists(self.hostsLocation) and \
				not os.access(self.hostsLocation, os.W_OK):
			raise SystemExit(\
					'ERROR: Do not have write permission for {0}'.format(\
					self.hostsLocation))
		with open(self.hostsLocation, 'w') as w:
			for line in self.unkownLines:
				w.write('{0}\n'.format(line))
			w.write('\n')
			for domain,ip in self.hosts.iteritems():
				w.write('{0} {1}\n'.format(ip, domain))

	def deleteHosts(self, domainList):
		for i in domainList:
			if i in self.hosts:
				del self.hosts[i]

	def deleteHostsFromFile(self, hostsfile):
		hosts, _ = self.parseHosts(hostsfile)
		self.deleteHosts(hosts.keys())

if __name__ == '__main__':
	if len(sys.argv) < 2:
		print USAGE
		raise SystemExit
	hosts = Hosts()
	#hosts.deleteHostsFromFile(sys.argv[1])
	hosts.update(sys.argv[1])
	hosts.writeHosts()