Async process execution in python.

async.py

from subprocess import Popen, PIPE
from thread import start_new_thread
import os, distutils.spawn 

def which(cmd):
  path = distutils.spawn.find_executable(cmd)
  if path == "None":
    raise Exception("DepMissing") 
  else:
  	return path 

def execute(cmd,WorkingDir):
	try:
	  print "Executing {0}".format(' '.join(cmd))
	  cmd_path = which(cmd[0])
	  cmd_args = cmd[1]
	  proc = Popen(cmd_path+cmd_args, cwd=WorkingDir, shell=True, stdout=PIPE, stderr=PIPE)
	  start_new_thread(handle_stderr, (proc.stdout,))
	except Exception as e:
		print "Is {0} installed and in PATH?".format(cmd[0])

def handle_stderr(stdout):
	while True:
		data = os.read(stdout.fileno(), 128*1024)
		if data != "":
			print(data)
		else:
			print "Done!"
			stdout.close()
			return