Dataclass on cassiobotarohttps://cassiobotaro.dev/en/tags/dataclass/Recent content in Dataclass on cassiobotaroHugoenSat, 25 Jul 2026 13:06:19 -0300Fully comparable objects with a single methodhttps://cassiobotaro.dev/en/posts/comparable-objects/Wed, 01 Jul 2026 00:00:00 +0000https://cassiobotaro.dev/en/posts/comparable-objects/<h2 id="the-problem"> The problem <a class="heading-link" href="#the-problem"> <i class="fa-solid fa-link" aria-hidden="true" title="Link to heading"></i> <span class="sr-only">Link to heading</span> </a> </h2> <p>For an object to respond to <code>&lt;</code>, <code>&lt;=</code>, <code>&gt;</code>, <code>&gt;=</code>, <code>==</code> and <code>!=</code>, Python expects you to implement <code>__lt__</code>, <code>__le__</code>, <code>__gt__</code>, <code>__ge__</code>, <code>__eq__</code> and <code>__ne__</code>. That is six nearly identical methods, tedious to write and easy to leave inconsistent (one says <code>a &lt; b</code> and another disagrees).</p> <h2 id="the-tip"> The tip <a class="heading-link" href="#the-tip"> <i class="fa-solid fa-link" aria-hidden="true" title="Link to heading"></i> <span class="sr-only">Link to heading</span> </a> </h2> <p>Two pieces cover everything:</p>The Money Objecthttps://cassiobotaro.dev/en/posts/the-money-object/Sun, 01 Mar 2026 00:00:00 +0000https://cassiobotaro.dev/en/posts/the-money-object/<p><img src="https://cassiobotaro.dev/images/dinheiro.png" alt="Money"></p> <h2 id="the-story"> The Story <a class="heading-link" href="#the-story"> <i class="fa-solid fa-link" aria-hidden="true" title="Link to heading"></i> <span class="sr-only">Link to heading</span> </a> </h2> <p>A while ago I took part in the hiring process of a fairly well known purple bank. I did not get in, but I got valuable feedback about the code I wrote. Putting that feedback together with things I learned afterwards, I decided to revisit the challenge and improve the implementation.</p> <p>One of the most significant improvements was creating a <code>Money</code> object, based on the pattern of the same name described by Martin Fowler in <em>Patterns of Enterprise Application Architecture</em> (PEAA).</p>