Why aren't Python dicts unified?
<p>After reading <a href="http://stackoverflow.com/questions/6602172/how-to-group-a-list-of-tuples-objects-by-similar-index-attribute-in-python">this question</a>, I noticed that S. Lott might have liked to use an “ordered defaultdict”, but it doesn't exist.  Now, I wonder: Why do we have so many dict classes in Python?</p>

<ul>
<li>dict</li>
<li>blist.sorteddict</li>
<li>collections.OrderedDict</li>
<li>collections.defaultdict</li>
<li>weakref.WeakKeyDictionary</li>
<li>weakref.WeakValueDictionary</li>
<li>others?</li>
</ul>

<p>Why not have something like this,</p>

<pre><code>dict(initializer=[], sorted=False, ordered=False, default=None, 
     weak_keys=False, weak_values=False)
</code></pre>

<p>that unifies everything, and provides every useful combination?</p>
