title: Max sum of elements in list
body: <p>I have a list of numbers. I need to choose a number from it, change its' sign, then take the total sum of the list, repeat if it does not produce the maximum sum.</p>
  <p>Take [5, -6, 2, -9] for example
  change 5 to -5 The sum is -18 which is not the maximum
  Change -9 to 9 The sum is 10 which is the maximum</p>
  <pre><code>lst = [5, -6, 2, -9]
  
  for i in range(len(lst)):
      lst[i] *= -1
      print (sum(lst))
  </code></pre>
  <p>this gives me all list multiplying by -1, I don't need that</p>
  <pre><code>import random
  
  test_list = [5, -6, 2, 9]
  random_num = random.choice(test_list)
  random_num *=-1
  print (random_num)
  </code></pre>
  <p>this gives me a random number with a reverse sign and then I don't know how to find the sum of the list</p>
  <p>I'm stuck :/ maybe someone has any ideas?</p>