How to delete all blank lines in the file with the help of python?
<p>For example, we have some file like that:</p>

<blockquote>
  <p>first line<br>
  second line
  <br><br>
  third line</p>
</blockquote>

<p>And in result we have to get:</p>

<blockquote>
  <p>first line<br>
  second line<br>
  third line</p>
</blockquote>

<p>Use ONLY python</p>
