title: Iterate through values of dataframe
body: <p>having a dataframe similar to the following</p>
  
  <pre><code>Country 00:00 00:30 01:00 ... 23:00 23:30
  SWE     10    15    32        12    57
  ITA     6     67    64        1     8
  USA     92    13    45        8     32
  ...
  </code></pre>
  
  <p>How can I e.g. loop through the items of USA (and incrementing by 10) while checking if the index is not bigger than 13:30? e.g.</p>
  
  <pre><code>for x in df[df.Country == 'USA]:
      if x.index != '13:30':
          x =+ 10
      else:
          break
  </code></pre>
  
  <p>Thanks so much!</p>