title: Why aren't Python sets hashable?
body: <p>I stumbled across a blog post detailing how to implement a powerset function in Python. So I went about trying my own way of doing it, and discovered that Python apparently cannot have a set of sets, since set is not hashable. This is irksome, since the definition of a powerset is that it is a set of sets, and I wanted to implement it using actual set operations.</p>
  
  <pre><code>&gt;&gt;&gt; set([ set() ])
  Traceback (most recent call last):
    File "&lt;stdin&gt;", line 1, in &lt;module&gt;
  TypeError: unhashable type: 'set'
  </code></pre>
  
  <p>Is there a good reason Python sets are not hashable?</p>