title: List comprehension - converting strings in one list, to integers in another
body: <p>Basically, I have a string given as follows: "56 65 74 100 99 68 86 180 90".</p>
  
  <p>I need to convert that in such a fashion that I will be able to sum each of the individual numbers making up the numbers above, i.e. 56 would become 5 + 6 would become 11.</p>
  
  <p>So far I have taken the following approach:</p>
  
  <pre><code>l = string.split()
  
  new_l = []
  
  # the below creates a list as follows: [['56'],['65'], ['74'] etc.]
  for x in l:
      new_l += [x.split()]
  
  # while this list comprehension simply splits the list up: [['5','6'], etc.]
  list_of_lists = [list(y) for x in new_l for y in x]
  
  # now, if I could convert the numbers in those inner lists into integers, 
  # I'd be getting where I need to
  
  # but for some reason, this list comprehension does not return what I need
  l_o_l = [[int(x)] for x in y for y in list_of_lists]
  </code></pre>
  
  <p>The last list comprehension simply returns a number of 9s and 0s and I can't for the life of me figure out why.</p>
  
  <p>Forgive my ignorance on this one, I've read a couple of explanations but they don't seem to be exactly what I'm looking for.</p>
  
  <p>All help greatly appreciated!</p>