title: Error can only concatenate list (not "str") to list
body: <p>My program is supposed to reverse the string inputted, print it then extract the numbers and print the numbers of the reversed string in a list.</p>
  
  <pre><code>def reverse_str(string):
      revstring =('')
      length=len(string)
      i = length - 1
      while i&gt;=0:
          revstring = revstring + string[i]
          i = i - 1
      return revstring
  def strip_digits(string):
      result = []
      for c in string:
          result = result + c
  string = raw_input("Enter a string-&gt;")
  new_str = reverse_str(string)
  print new_str
  numberless_str  = strip_digits(string)
  print numberless_str
  </code></pre>