title: How to get a unique value from a list in python
body: <p>Imagine I have this list:</p>
  <pre><code>list = ['a','a','b','a']
  </code></pre>
  <p>I would like to do something like this:</p>
  <pre><code>print(unique(list))
  </code></pre>
  <p>to retrieve the unique item(s), so python will output <code>b</code>. How could I do this?</p>