title: How can i retrieve modified documents after an update operation in mongodb with pymongo?
body: <p>I'm using an update operation with upsert. I want to retrieve all documents that have been modified after an update.</p>
  
  <pre><code>for key in categories_links:
      collection.update({"name" : key}, {"name": key ,"url" : categories_links[key]}, True)
  </code></pre>