Run commands in parallel with a limited pool

batch_run.py

num_proc = 8

procs = []
running = []
for command in commands: 
  while (sum(running) >= num_proc): 
    for i, proc in enumerate(procs): 
      running[i] = (proc.poll() is None)
    time.sleep(1.0)
  procs.append(subprocess.Popen(command, shell=True))
  running.append(True)
  
while (sum(running) > 0): 
  for i, proc in enumerate(procs): 
    running[i] = (proc.poll() is None)
  time.sleep(1.0)