title: AttributeError: 'float' object has no attribute 'append' when trying to append values to existing key
body: <p>Trying to append float values to the same key in defaultdic type dictionary.</p>
  <pre class="lang-py prettyprint-override"><code>from collection import defaultdict
  
  new_dict= defaultdict(list)
  
  for row in list_dict:
      acct=row[acct]
      time_spent= float(row[time_spent])
  
      if (acct not in new_dict):
          new_dict[acct] = time_spent
      else:
          new_dict[acct].append(time_spent)
  </code></pre>
  <p>gives me error:</p>
  <pre class="lang-py prettyprint-override"><code>AttributeError: 'float' object has no attribute 'append'
  </code></pre>
  <p>If I remove float,</p>
  <pre class="lang-py prettyprint-override"><code>time_spent= float(row[time_spent])
  </code></pre>
  <p>gives me,</p>
  <pre class="lang-py prettyprint-override"><code>AttributeError: 'str' object has no attribute 'append'
  </code></pre>
  <p>I have to add those time_spent in the list of values later so I would like them to be float.</p>