title: open() in Python does not create a file if it doesn't exist
body: <p>What is the best way to open a file as read/write if it exists, or if it does not, then create it and open it as read/write? From what I read, <code>file = open('myfile.dat', 'rw')</code> should do this, right?</p>
  
  <p>It is not working for me (Python 2.6.2) and I'm wondering if it is a version problem, or not supposed to work like that or what.</p>
  
  <p>The bottom line is, I just need a solution for the problem. I am curious about the other stuff, but all I need is a nice way to do the opening part.</p>
  
  <p>The enclosing directory was writeable by user and group, not other (I'm on a Linux system... so permissions 775 in other words), and the exact error was:</p>
  
  <blockquote>
    <p>IOError: no such file or directory.</p>
  </blockquote>