title: The real count is different from the result of collection.find() in MongoDB
body: <p>Recently, I wrote a tiny app to query data from MongoDB with pymongo. The code as following shown</p>
  
  <pre><code>colls = collection.find({'created': {'$gt': datetime.datetime(2014, 9, 14, 10),
                                       '$lt': datetime.datetime(2014, 9, 14, 17)}},
                          {'created':1, '_id': 0})
  print 'Totally count is ', colls.count()
  </code></pre>
  
  <p>So far, everything is okay. However,</p>
  
  <pre><code>results = []
  for item in colls:
      results.append(item)
  </code></pre>
  
  <p>I found that the length of <strong>results</strong> is less than <strong>colls.count()</strong>. It was so strange? Why they are different?</p>