title: use pickle to save dictionary in python
body: <p>I have a file <code>hash_db.pickle</code> that when I created it I saved a dictionary on it:</p>
  
  <pre><code>v = {hash_value:{"file name":file_name,"file size":file_size,"last scanned time":scanned_time}}
  
  {123dfre345:{"file name":calc.pdf,"file size":234,"last scanned time":12:23 24/12/2013}}
  {3gcdshj754:{"file name":star.pdf,"file size":10,"last scanned time":10:30 10/10/2013}}
  </code></pre>
  
  <p>so if I want to change from the file only <code>last scanned time</code> for <code>3gcdshj754</code></p>
  
  <p>how could I do that?</p>