title: SQLAlchemy: selecting which columns of an object in a query
body: <p>Is it possible to control which columns are queried in the query method of SQLAlchemy, while still returning instances of the object you are querying (albeit partially populated)?</p>
  
  <p>Or is it necessary for SQLAlchemy to perform a <code>SELECT *</code> to map to an object?</p>
  
  <p>(I do know that querying individual columns is available, but it does not map the result to an object, only to a component of a named tuple).</p>
  
  <p>For example, if the User object has the attributes userid, name, password, and bio, but you want the query to only fill in userid and name for the objects it returns:</p>
  
  <pre><code># hypothetical syntax, of course:
  for u in session.query(User.columns[userid, name]).all():
      print u
  </code></pre>
  
  <p>would print:</p>
  
  <pre><code>&lt;User(1, 'bob', None, None)&gt; 
  &lt;User(2, 'joe', None, None)&gt;
  ...
  </code></pre>
  
  <p>Is this possible; if so, how?</p>