title: group by week in pandas
body: <p>I'm having this data frame:</p>
  <pre><code>Name   Date    Quantity
  Apple  07/11/17  20
  orange 07/14/17  20
  Apple  07/14/17  70
  Orange 07/25/17  40
  Apple  07/20/17  30
  </code></pre>
  <p>I want to aggregate this by <code>Name</code> and <code>Date</code> to get sum of quantities
  Details:</p>
  <p><strong>Date</strong>: Group, the result should be at the beginning of the week (or just on Monday)</p>
  <p><strong>Quantity</strong>: Sum, if two or more records have same Name and Date (if falls on same interval)</p>
  <p>The desired output is given below:</p>
  <pre><code>Name   Date    Quantity
  Apple  07/10/17  90
  orange 07/10/17  20
  Apple  07/17/17  30
  orange 07/24/17  40
  </code></pre>
  <p><em><strong>Thanks in advance</strong></em></p>