title: problem with if else loop for a month and days problem
body: <p>why do I get the wrong output for the code below, I've put the output below</p>
  <p>(some might suggest using date-time module, I'm going with this method due to some complications with the main program)</p>
  <pre><code>    months = [1,2,3,4,5,6,7,8,9,10,11,12]
      for month in months:
          if month == {1,3,5,7,9,11}:
              days= 31
              print(days)
          elif month == {4,6,8,10,12}:
              days = 30
              print(days)
          else :
              days = 28
              print(days)
  </code></pre>
  <p>I get this output</p>
  <pre><code>    28
      28
      28
      28
      28
      28
      28
      28
      28
      28
      28
      28
  </code></pre>