Polling script for my netmon tool

polling.py

import sqlite3, datetime, subprocess, time
from multiprocessing.pool import ThreadPool

class Device(object):
	instances = []
	def __init__(self, id, hostname, type, ip, subnet, building, online, last_seen):
		self.id = id
		self.hostname = hostname
		self.type = type
		self.ip_address = ip
		self.subnet = subnet
		self.building = building
		self.online = online
		self.last_seen = last_seen
		Device.instances.append(self)
		
	def __str__(self):
		return self.hostname
		
	def ping(self): #this probably only works on windows
		proc = subprocess.Popen(['ping', '-n', '1', self.ip_address], stdout=subprocess.PIPE)
		stdout, stderr = proc.communicate()
		if proc.returncode == 0:
			self.online = 'True'
			self.last_seen = str(datetime.datetime.now())
		else:
			self.online = 'False'
			
	def all():
		return str(Device.instances)
		
	def is_online(self):
		return self.online

	def report_down():
		print('{0:15} {1:8} {2:8} {3:20}'.format('Device', 'Location', 'Status', 'Last Seen'))
		for instance in Device.instances:
			if instance.online == 'False':
				print('{0:15} {1:8} {2:8} {3:20}'.format(instance.ip_address, instance.building, 'Offline', instance.last_seen))

def build_objects():
	conn = sqlite3.connect('nsbmon.db')
	c = conn.cursor()
	devices = c.execute("SELECT * FROM monitor_networkdevice")
	for row in devices.fetchall():
		Device(id = row[0],
			hostname = row[1],
			type = row[2],
			ip = row[3],
			subnet = row[4],
			building = row[5],
			online = row[6],
			last_seen = row[7])
	c.close()

def poll_collector():
	poll_data = []
	for instance in Device.instances:
		poll_data.append((instance.online, instance.last_seen, instance.id))
	return poll_data
		
def update_sql_from_objects():
	conn = sqlite3.connect('nsbmon.db')
	c = conn.cursor()	
	c.executemany('UPDATE monitor_networkdevice SET online = ?, last_seen = ? WHERE id= ?', poll_collector())
	print('{} total rows updated in database.'.format(conn.total_changes))
	conn.commit()
	c.close()	

def poller(threads=250):
	print('Starting poller, will loop forever. Press Esc to break.')
	try:
		while True:
			start_time = datetime.datetime.now()
			pool = ThreadPool(threads)
			pool.map(Device.ping, Device.instances)
			pool.close()
			pool.join()
			end_time = datetime.datetime.now()
			print('Polled {} devices in {}.'.format(len(Device.instances), (end_time-start_time)))
			update_sql_from_objects()
			print('Sleeping for 3 mins.')
			time.sleep(180)
	except KeyboardInterrupt:
		pass
		
build_objects()
poller()