title: How to set value NULL to a field in SQLAlchemy?
body: <p>I've a <code>Table</code> called <code>journals</code> in SqlAlchemy that has one of the following Columns:</p>
  
  <pre><code>Column('type', String(128))
  </code></pre>
  
  <p>Then I've <code>mapper</code> that maps <code>journals</code> to <code>Journals</code> python class:</p>
  
  <pre><code>mapper(Journals, journals);
  </code></pre>
  
  <p>I want to insert a new row in <code>journals</code> and set <code>type</code> to <code>NULL</code>.</p>
  
  <p>What would be the corresponding Python type to NULL?</p>
  
  <p>Here's example:</p>
  
  <pre><code>self.type = NULL;
  </code></pre>
  
  <p>There is no <code>NULL</code> type in Python so I don't know how to do it.</p>