title: How to fix NameError: name 'author' is not defined when running python script
body: <p>I am trying to open up this on the terminal on my mac, but I keep getting name 'author' not defined when it clearly is. </p>
  
  <pre><code>def bibformat_mla(author, title, city, publisher, year):
      author = input("enter author: ")
      title = input("enter title: ")
      city = input("enter city: ")
      publisher = input("enter publisher: ")
      year = input("enter year: ")
      answer = author + ' , ' + title + ' , ' + city + ': ' + publisher + ', ' + year
      return answer
  
  
  bibformat_mla(author, title, city, publisher, year)
  'author, title, city: publisher, year'
  
  bibformat_mla("Jake, Matt", "Open Data ", "Winnipeg", "AU Press", 2013)
   'Morin, Pat. Open Data Structures. Winnipeg: AU Press, 2013'
  </code></pre>