Python: Appending to a list in a dictionary
<p>SO,</p>

<p>Having a case of the Monday's and none of my references are helping me out.</p>

<p>I have a file formatted like this:</p>

<pre><code>x1    y1    z1
x1    y2    z2
x2    y3    z3
</code></pre>

<p>I would like to make a dictionary formatted like this: {x1: [[y1, z1], [y2,z2]], x2: [y3,z3]} but I'm getting stuck on an efficient way to do this. Help?</p>
