title: adding a value to a set in a dictionary
body: <pre><code>def CreateDataBaseByActor(file):
     dataBase = dict()
     set = {}
     f = open(file,"r")
     for line in f:
         set = line.split(', ')
         for movie in set[1:]:
             dataBase[movie] = set[0]
     return dataBase
  </code></pre>
  
  <blockquote>
    <p>i have a file that each line is written by the format: actor_name, movie1, movie2, movie3...
    example: </p>
  </blockquote>
  
  <ul>
  <li><p>Sylvester Stallone, Rocky, Rambo, Assassins</p></li>
  <li><p>Julianne Moore, Assassins, Hannibal</p>
  
  <blockquote>
    <p>the problem is that when i try to add to a movie, another actor name (for example: in the first line, the key - Assassins- has the value Sylvester Stallone, and in the second line value of - Assassin - is replaced instead of added)</p>
  </blockquote></li>
  </ul>