title: Python if_py and VIM: BufAdd, inserting stuff into a new buffer
body: <p>When I open a buffer (via :tabnew or any other way), if there
  is no filename associated with the buffer, I'd like to insert
  some default text (recently opened files).</p>
  
  <pre><code>au BufAdd * call My_dir(expand("&lt;afile&gt;"))
  
  function! My_dir(fname)
  python &lt;&lt; EOF
  import vim
  blah = vim.eval('a:fname')
  if str(blah) == 'None':
      cb = vim.current.buffer
      cb.append("yuck")
  EOF
  endfunction
  </code></pre>
  
  <p>The trouble is that, fname will be 'None' but current.buffer is 
  the previous buffer I was in! How do I get the buffer I just 
  opened so I can stick stuff in it??</p>