#!/usr/bin/python
#change number 6 to desired number of parallel processes
#original credit: Kovid Goyal, Calibre author.

import os, time, glob, subprocess

files = glob.glob('*.epub')

workers = []
while files or workers:
	while len(workers) < 6 and files:
		f = files[0]
		files = files[1:]
		w = subprocess.Popen(['/Applications/calibre.app/Contents/MacOS/ebook-convert', f, os.path.splitext(f)[0]+'.mobi'])
		workers.append(w)
	for w in list(workers):
		if w.poll() is not None:
			workers.remove(w)
	time.sleep(0.1)