title: Python, running command line tools in parallel
body: <p>I am using Python as a script language to do some data processing and call command-line tools for number crunching. I wish to run command-line tools in parallel since they are independent with each other. When one command-line tool is finished, I can collect its results from the output file. So I also need some synchronization mechanism to notify my main Python program that one task is finished so that the result could be parsed into my main program. </p>
  
  <p>Currently, I use <code>os.system()</code>, which works fine for one-thread, but cannot be parallelized. </p>
  
  <p>Thanks!</p>