title: Pandas: How to extract and calculate the number of “hour” per row in a Dataframe
body: <p>I have a data frame representing the schedule of some restaurants in a week.</p>
  <ul>
  <li><strong>What i want to do is to add a column <code>week_hours</code> to my initial Dataframe <code>df</code> that represents the total number of hours the restaurant is open per week.</strong></li>
  </ul>
  <p><strong>note</strong> : the value 0 simply means that the restaurant is closed that day.</p>
  <pre class="lang-py prettyprint-override"><code>data = {
          'restaurant_id':  ['1', '2','3'],
          'Monday':  ['11:0-20:0', '11:30-22:0','11:30-21:0'],
          'Tuesday':  ['11:0-20:0', '11:30-22:0','11:30-22:0'],
          'Wednesday':  ['11:0-20:0', '11:30-22:0','11:30-21:0'],
          'Thursday':  ['11:0-20:0', '11:30-22:0','11:30-21:0'],
          'Friday':  ['11:0-22:0', '11:30-22:0','11:30-21:0'],
          'Saturday':  ['11:0-22:0', '12:0-22:0','0'],
          'Sunday':  ['11:0-17:0', '16:30-21:30','11:30-21:0',],
  
          }
  
  df = pd.DataFrame (data, columns = ['restaurant_id','Monday','Tuesday','Wednesday','Thursday','Friday','Saturday','Sunday',])
  df.head()
  
  </code></pre>
  <p>What could be a simple syntax to achieve this?</p>