title: python 3 adding multiple values under same key in dictionary
body: <p>i have a problem with my code, tried looking up how to fix it and tried multiple methods but its just not going</p>
  
  <p>Here is what i got:</p>
  
  <pre><code>with open("people-data.txt") as f:
  
  children= {}
  for line in f.readlines():
      parent, child = line.split("-&gt;")
      children[parent] = child
  </code></pre>
  
  <p>I tried using: <code>children[parent].append(child)</code> and other things.</p>
  
  <p>My file looks like this:</p>
  
  <pre><code>Mary-&gt;Patricia
  Mary-&gt;Lisa
  Patricia-&gt;Barbara
  </code></pre>
  
  <p>What I would like is when I use <code>children[Mary]</code> I get <code>['Patricia', 'Lisa']</code> but what my code does is give my just <code>'Lisa'</code> and overrides <code>'Patricia'</code>.</p>