title: Missing 1 Required Keyword-Only Argument
body: <p>When I try to enter a dataframe as a function parameter in Python 3.6, I'm getting the error 'Missing 1 Required Keyword-Only Argument' for the following function, where df is a dataframe and rel_change is an array:</p>
  
  <pre><code>def get_mu(*rel_change, df):
  
      row_count = len(df.index)
      print("mu count")
      print(row_count)
      mu_sum = 0
      for i in range (0, len(rel_change)):
          mu_sum += rel_change[i]
      mu = (mu_sum) / row_count
      return mu
  </code></pre>
  
  <p>Then I access it like</p>
  
  <pre><code>mu = get_mu(g, df) 
  </code></pre>
  
  <p>which gives the error.</p>
  
  <p>I've also tried writing the dataframe access in another function that just calculates row_count, and passing that into mu, but that gives the same error. 
  What could I be doing wrong?</p>