title: Get unique combinations of elements from a python list
body: <p>Edit:
  This is not a exact duplicate of <a href="https://stackoverflow.com/questions/464864/python-code-to-pick-out-all-possible-combinations-from-a-list">How to get all possible combinations of a list’s elements?</a></p>
  
  <p>This topic is about finding unique combinations while the other topic is about finding ALL combinations.</p>
  
  <p>If I have a python list:</p>
  
  <pre><code> L = [1,2,3,4]
  </code></pre>
  
  <p>what's the best way to get all the possible <em>unique combinations</em> of 3 elements from the list like below:</p>
  
  <pre><code>["1,2,3", "1,2,4", "2,3,4", "3,4,1"]
  </code></pre>
  
  <p>The order of the elements in the combinations doesn't matter. For example, <code>"1,2,3"</code> and <code>"3,2,1"</code> will be considered the same combination.</p>
  
  <p>I can probably write a few loops to do this but I think there might be a one-liner which can do the same.</p>