title: How to access environmental variables from docker in python?
body: <p>I have a Docker file which list environmental variable as follows:</p>
  <pre><code>ENV WORKGROUP &quot;my-workgroup&quot;
  </code></pre>
  <p>In python file I am accessing it as follows:</p>
  <pre><code>os.environ['WORKGROUP']
  </code></pre>
  <p>When I build the docker it fails with the following error:</p>
  <pre><code>KeyError: 'WORK_GROUP'
  </code></pre>
  <p>The reason is some environmental variables have some default values which I need to set in docker. I can override these inside docker run command when needed. Any idea how can I achieve such a scenario. Thanks.</p>