Processing a list of lists
<p>I have a list of lists, say:</p>

<pre><code>    arr = [[1, 2], [1, 3], [1, 4]]
</code></pre>

<p>I would like to append 100 to each of the inner lists. Output for the above example would be:</p>

<pre><code>    arr = [[1, 2, 100], [1, 3, 100], [1, 4, 100]]
</code></pre>

<p>I can of course do:</p>

<pre><code>    for elem in arr:
        elem.append(100)
</code></pre>

<p>But is there something more pythonic that can be done? Why does the following not work:</p>

<pre><code>    arr = [elem.append(100) for elem in arr]
</code></pre>
