title: how to convert a list of strings into a list of sublists of the individual characters in the strings?
body: <p>So I am starting with:</p>
  
  <pre><code>['BLUE', 'ORANGE', 'YELLOW', 'GREEN', 'BLACK', 'PURPLE', 'BROWN']
  </code></pre>
  
  <p>and I want:</p>
  
  <pre><code>[['B', 'L', 'U', 'E'], ['O', 'R', 'A', 'N', 'G', 'E'], ['Y', 'E', 'L', 'L', 'O', 'W'], ['G', 'R', 'E', 'E', 'N'], ['B','L', 'A', 'C', 'K'], ['P', 'U', 'R', 'P', 'L', 'E'], ['B', 'R', 'O', 'W','N']]
  </code></pre>
  
  <p>I tried this because it looked like it would produce what I wanted but it keeps telling me I have an error. AttributeError: 'NoneType' object has no attribute 'append':</p>
  
  <pre><code>first_list = ['BLUE', 'ORANGE', 'YELLOW', 'GREEN', 'BLACK', 'PURPLE', 'BROWN']
  list_1 = []
  
  for i in range (len(first_list)):
      list_1 = list_1.append(list(first_list[i]))
  
  return list_1
  </code></pre>
  
  <p>I keep having trouble using the ".append" and keep using "+" in other iterations but that just gives me a long list of all the characters instead of a list of sublists of characters. Thank you for any help or advice.</p>