Check if file is open for any file type
<p>The Python File Type documentation gives <code>file.closed</code> as a</p>

<blockquote>
  <p>bool indicating the current state of the file object. This is a read-only attribute; the <code>close()</code> method changes the value. It may not be available on all file-like objects.</p>
</blockquote>

<p>Given that it's not guaranteed to be available on all file-like objects, is there another (better?) method of checking whether I've already got the file open, before trying to re-open it? </p>
