How to get a list with elements that are contained in two other lists?
<p>We have two lists:</p>

<pre><code>a=['1','2','3','4']
b=['2','3','4','5']
</code></pre>

<p>How to get a list with elements that are contained in both lists:</p>

<pre><code>a_and_b=['2','3','4']
</code></pre>

<p>and a list with elements that are contained only in one list, but not the other:</p>

<pre><code>only_a=['1']
only_b=['5']
</code></pre>

<p>Yes, I can use cycles, but it's lame =)</p>
