Find position where the member of two lists differs : <p>I have the following two lists of strings with the same size:</p>

<pre><code>l1 = ['foo', 'foo','bar','cho']
l2 = ['foo', 'qux','bar','cxx']
              *           *
</code></pre>

<p>What I want to do is to find the position where the members differs,
yielding:</p>

<pre><code>1, 3
</code></pre>

<p>How can we do that?</p>
