title: Using a while loop to compute the sum of integers from two numbers
body: <p>I'm having some trouble with a homework problem on MyPytutor which is asking me to write a function sum_from_to(start, end) that uses a while loop to compute the sum of the integers from start up to, but not including end. </p>
  
  <p>The given code is:</p>
  
  <pre><code>def sum_from_to(start, end):
  """Return the sum of the integers from start up to but not including end.
  
  sum_from_to(int, int) -&gt; int
  """
  # add your code here: use a while loop
  </code></pre>
  
  <p>Examples:</p>
  
  <ul>
  <li>sum_from_to(3, 7) should evaluate to 18 (i.e. 3+4+5+6).</li>
  <li>sum_from_to(3, 3) should evaluate to 0.</li>
  </ul>
  
  <p>How would I approach this? I've seen this same question from half a year ago but it was never resolved. Any help would be greatly appreciated as I'm really stuck on this!</p>