title: Why use Python's `open()` function to open file descriptors?
body: <p>Python's builtin <code>open()</code> function <a href="https://docs.python.org/3/library/functions.html#oct" rel="nofollow noreferrer">documentation</a> reads (emphasis mine)</p>
  
  <blockquote>
    <p><em>file</em> is a path-like object giving the pathname (absolute or relative to the current working directory) of the file to be opened or <strong>an integer file descriptor of the file to be wrapped</strong>. (If a file descriptor is given, it is closed when the returned I/O object is closed, unless closefd is set to <code>False</code>.)</p>
  </blockquote>
  
  <p>It's not clear to me to which file descriptor's process it is referring to, nor if it is possible to refer to the file descriptor's of any process or how to do it.</p>
  
  <p>Experimenting for a bit in an interactive shell, I figured out the process it is referring to is the shell itself.</p>
  
  <p>My question is: how is it that this is useful in a way that passing strings isn't?</p>