returning matches from an unknown number of python lists
<p>I have a list which contains 1-5 lists within it. I want to return only the values which appear in all the lists. I can easily create an exception for it there is only one list, but I can't think of a way round it when there are an multiple (unknown number of) lists. For example:</p>

<pre><code>[[1,2,3,4],[2,3,7,8],[2,3,6,9],[1,2,5,7]]
</code></pre>

<p>would only return 2, because it's the only list item to appear in all the sub-lists</p>

<p>How can I achieve this?</p>
