Semaphore example

graburl.py

import threading, os, re, sqlite3, sys
from subprocess import *

class GrabUrl(threading.Thread):
	def __init__(self, arg0):
		threading.Thread.__init__(self)
		self.host=arg0
	def run(self):
		print "Getting "  + self.host
		arr=['wget', self.host]
		p1=Popen(arr, shell=False)
		waiter=Process_Waiter(p1, self.host)
		waiter.start()



class Handler(threading.Thread):
	def __init__(self):
		threading.Thread.__init__(self)
	def run(self):
		for i in hosts:
			pool.acquire()
			graburl=GrabUrl(i)
			graburl.setDaemon(True)
			graburl.start()

class Process_Waiter(threading.Thread):
	def __init__(self, arg0, arg1):
		threading.Thread.__init__(self)
		self.p1=arg0
		self.host=arg1
	def run(self):
		try:
			self.p1.wait()
		finally:
			print "exiting " + self.host
			pool.release()

maxconn=2
pool=threading.BoundedSemaphore(value=maxconn)
hosts=["http://google.com", "http://amazon.com", "http://apple.com", "http://aol.com", "http://yahoo.com", "http://yahoo.co.uk", "http://ebay.com"]
handler=Handler()
handler.start()
handler.join()
print "exiting main"