title: How do I run some python code in another process?
body: <p>I want to start, from Python, some other Python code, preferably a function, but in <strong>another process</strong>. </p>
  
  <p>It is mandatory to run this in another process, because I want to run some concurrency tests, like opening a file that was opened exclusively by the parent process (this has to fail).</p>
  
  <p>Requirements:</p>
  
  <ul>
  <li>multiplatform: linux, osx, windows</li>
  <li>compatible with Python 2.6-3.x</li>
  </ul>