title: Python - Exclusive attribute value for object?
body: <p>Let say I have this class:</p>
  
  <pre><code>class A(object):
   def __init__(self, one=None):
     self.one = one
  </code></pre>
  
  <p>So every time you create <code>A</code> object, you can assign <code>one</code> attribute. But only the last object assigned not false value gets to keep it.</p>
  
  <p>For example:</p>
  
  <pre><code>a = A('a')
  b = A('b')
  c = A()
  print a
  print b
  print c
  ----
  None
  b
  None
  </code></pre>
  
  <p>Now these objects are also actual records (rows) in database, so those could be accessed later.</p>
  
  <p>What could be a good pattern (if there is) to set such attribute dynamically (unsetting attribute for older objects)?</p>