title: Naming convention in Collections: why are some lowercase and others CapWords?
body: <p>Why the mixture of lowercase and UpperCamelCase? </p>
  
  <pre><code>namedtuple
  deque   
  Counter 
  OrderedDict
  defaultdict
  </code></pre>
  
  <p>Why <code>collections</code> instead of <code>Collections</code>?</p>
  
  <p>I sometimes do this for example:</p>
  
  <pre><code>from collections import default_dict
  </code></pre>
  
  <p>by mistake. What rule of thumb can I use to avoid such mistakes in the future?</p>