擅长：python、mysql、java
<p>有一个<code>count</code>操作。</p>
<p><a href="https://developers.google.com/appengine/docs/python/ndb/queryclass#Query_count" rel="noreferrer">https://developers.google.com/appengine/docs/python/ndb/queryclass#Query_count</a></p>
<p><code>count(limit=None, **q_options)</code></p>
<blockquote>
<p>Returns the number of query results, up
to a limit. This returns the same result as len(q.fetch(limit)) but
more efficiently.</p>
</blockquote>
