title: Make Strings In List Uppercase - Python 3
body: <p>I'm in the process of learning python and with a practical example I've come across a problem I cant seem to find the solution for.
  The error I get with the following code is 
  <code>'list' object has to attribute 'upper'</code>. </p>
  
  <pre><code>def to_upper(oldList):
      newList = []
      newList.append(oldList.upper())
  
  words = ['stone', 'cloud', 'dream', 'sky']
  words2 = (to_upper(words))
  print (words2)
  </code></pre>