title: How to sum columns of an array in Python
body: <p>How do I add up all of the values of a column in a python array? Ideally I want to do this without importing any additional libraries.</p>
  
  <pre><code>input_val = [[1, 2, 3, 4, 5],
               [1, 2, 3, 4, 5],
               [1, 2, 3, 4, 5]]
  
  output_val = [3, 6, 9, 12, 15]
  </code></pre>
  
  <p>I know I this can be done in a nested for loop, wondering if there was a better way (like a list comprehension)?</p>