Counting removed items in a Set in Python
<p>Given two sets</p>

<pre><code>a = [5,3,4,1,2,6,7]
b = [1,2,4,9]
c = set(a) - set(b)
# c -&gt; [5,3,6,7]
</code></pre>

<p>is it possible to count how many items were removed from set 'a' ?</p>
