Set function in Python 2.2
<p>I have a problem regarding set in Python 2.2.
Currently I am just comparing between two lists like so:</p>

<pre><code>temp3 = set(list1) - set(list2)
</code></pre>

<p>But it keeps prompting me that set isn't define. I used 2.7 to create the program. 
Updating software is not an option sadly.
Is there an alternative I can use?</p>
