title: Pandas Python How to get sum of all other rows except the row that contains the sum
body: <p>I want to create a column like the 'sum' below from 'col1', where all elements of column 'sum' are the sum of the other rows of col1</p>
  <pre class="lang-py prettyprint-override"><code>col1    sum
  1       9 (3+5+1)
  3       7
  5       5
  1       9
  </code></pre>