title: How can I find the union on a list of sets in Python?
body: <p>This is the input:  </p>
  
  <pre><code>x = [{1, 2, 3}, {2, 3, 4}, {3, 4, 5}]
  </code></pre>
  
  <p>and the output should be:</p>
  
  <pre><code>{1, 2, 3, 4, 5}
  </code></pre>
  
  <p>I tried to use <code>set().union(x)</code> but this is the error I'm getting:</p>
  
  <pre class="lang-none prettyprint-override"><code>Traceback (most recent call last):
    File "&lt;stdin&gt;", line 1, in &lt;module&gt;
  TypeError: unhashable type: 'set'
  </code></pre>