title: How to extract application ID from the PySpark context
body: <p>A <a href="https://stackoverflow.com/q/23378407/850781">previous question</a> recommends <code>sc.applicationId</code>, but it is <em>not</em> present in <code>PySpark</code>, only in <code>scala</code>.</p>
  
  <p>So, how do I figure out the application id (for <code>yarn</code>) of my PySpark process?</p>