title: Why does creating a frozenset out of a list in python convert the list?
body: <p>In python, when creating a frozenset out of a list, for example:</p>
  
  <pre><code>a=[1,2,3]
  b=frozenset(a)
  </code></pre>
  
  <p>iterating over the items in 'a' iterates over 3 items, as expected, yet iterating over the items in 'b' also iterates over the same 3 items. I expected 'b' to contain only 1 item, the list 'a'. Why does this happen?</p>