Assigning values to elements of list
<p>When I have a for loop:</p>

<pre><code>for row in list:
    row = something_or_other
</code></pre>

<p>It seems that sometimes I can assign a value (or append/extend etc.) directly to <code>row</code> and the <code>list</code> changes accordingly, and sometimes I have to do something roundabout like:</p>

<pre><code>for row in list:
    list[list.index(row)] = something_or_other
</code></pre>

<p>What gives?!?</p>
