How do I loop through relationships in a list only once?
<p>I have a list of users:</p>

<pre><code>users = [1,2,3,4,5]
</code></pre>

<p>I want to compute a relationship between them:</p>

<pre><code>score = compatibility( user[0], user[1] )
</code></pre>

<p>How do I loop over users so that a relationship between users are computed only once?</p>
