title: Subtract pandas columns from a specified column
body: <p>How can I dynamically subtract values in multiple pandas dataframe columns from a specified column. In this case, how can I subtract columns A, B, and C from deposit and place the value in the corresponding A, B, and C columns.</p>
  
  <pre><code>   date         deposit       A                 B           C
  0  2017-01-15   12            5                 10          12
  1  2017-01-16   20            10                4           32
  2  2017-01-17   5             50                10          18
  3  2017-01-18   22            15                20          12
  </code></pre>
  
  <p>should produce:</p>
  
  <pre><code>   date         deposit       A                 B           C
  0  2017-01-15   12            7                 2           0
  1  2017-01-16   20            10                16         -12
  2  2017-01-17   5            -45               -5          -13
  3  2017-01-18   22            7                 2           10
  </code></pre>