title: How to check if a user exists in a GNU/Linux OS using Python?
body: <p>What is the easiest way to check the existence of a user on a GNU/Linux OS, using Python?</p>
  
  <p>Anything better than issuing <code>ls ~login-name</code> and checking the exit code?</p>
  
  <p>And if running under Windows?</p>