title: How to set environment variables in Heroku for a Flask app?
body: <p>I have a Flask application that uses different configuration files for development and production environments. The relevant piece of code is this:</p>
  <pre><code>app.config.from_object('config.dev')
  app.config.from_envvar('SPOTPIX_SETTINGS', silent=True)
  </code></pre>
  <p>When I'm developing in my local server, the configurations are taken from config.dev, but when I push the code to Heroku, I would like to set the <code>SPOTPIX_SETTINGS</code> environment variable to point to the 'config.prod' file. This can be done in the Heroku command line client like so:</p>
  <pre><code>heroku config:set SPOTPIX_SETTINGS= 
  </code></pre>
  <p>However, I have no clue what should I write to the right of the equals sign, as I can't assign the absolute path of the production configuration file to the environment variable, because this is not the same in Heroku as it is in my development machine.</p>