title: How to remove lines that has a duplicated value in a column from a CSV file?
body: <p>I have a txt file with this format:</p>
  <pre class="lang-none prettyprint-override"><code> - 01, Spain
   - 02, USA
   - 03, India
   - 01, Italy
   - 01, Portugal
   - 04, Brasil
  </code></pre>
  <p>I need to check if the numbers are repeated. In this example, the number &quot;01&quot; has Spain, Italy and Portugal. If two or more lines have the same number, I  need to keep only the first of the repeated number and get rid of the others. It would show this in the output file:</p>
  <pre class="lang-none prettyprint-override"><code> - 01, Spain
   - 02, USA
   - 03, India
   - 04, Brasil
  </code></pre>