title: Bare forward slash in Python function definition?
body: <p>In the <a href="https://docs.python.org/3.8/faq/programming.html#how-do-i-write-a-function-with-output-parameters-call-by-reference" rel="noreferrer">Python 3.8 Programming FAQ</a>, I saw the following function definition:</p>
  
  <pre><code>class callByRef:
      def __init__(self, /, **args):
          for key, value in args.items():
              setattr(self, key, value)
  </code></pre>
  
  <p>This is missing in <a href="https://docs.python.org/3.7/faq/programming.html#how-do-i-write-a-function-with-output-parameters-call-by-reference" rel="noreferrer">the Python 3.7 version</a>:</p>
  
  <pre><code>class callByRef:
      def __init__(self, **args):
          for (key, value) in args.items():
              setattr(self, key, value)
  </code></pre>
  
  <p>What is this new <code>/</code> syntax?</p>
  
  <p>How does it relate to a <code>/</code> appearing in <code>help()</code> output?</p>
  
  <hr>
  
  <p>Note: <a href="https://stackoverflow.com/q/24735311/5353461">this</a> and <a href="https://stackoverflow.com/questions/28243832/what-is-the-meaning-of-a-forward-slash-in-a-python-method-signature-as-show">this</a> question are about <code>help()</code> <em>annotation</em>, whereas this question is about new syntax and any differences to the <code>help()</code> annotation.</p>