title: Append to a file after nth byte in python
body: <p>I need to <strong>append</strong> to the file after nth byte without deleting the previous content.</p>
  
  <p>For Example,
  If I have a file containing : "Hello World"<br>
  and I seek to position(5) to write " this" I should get <br> 
  "Hello this world"</p>
  
  <p>Is there any mode in which I should open the file??</p>
  
  <p>Currently my code replace the characters <br>
  and gives "Hello thisd"</p>
  
  <pre><code>&gt;&gt;&gt; f = open("1.in",'rw+')
  &gt;&gt;&gt; f.seek(5)
  &gt;&gt;&gt; f.write(' this')
  &gt;&gt;&gt; f.close()
  </code></pre>
  
  <p>any suggestions?</p>