title: Delete unused packages from requirements file
body: <p>Is there any easy way to delete no-more-using packages from <strong>requirements</strong> file?</p>
  
  <p>I wrote a bash script for this task but, it doesn't work as I expected. Because, some packages are not used following their PyPI project names. For example;</p>
  
  <pre><code>dj-database-url
  </code></pre>
  
  <p>package is used as </p>
  
  <pre><code>dj_database_url
  </code></pre>
  
  <p>My project has many packages in its own requirements file, so, searching them one-by-one is too messy, error-prone and takes too much time. As I searched, IDEs don't have this property, yet.</p>