title: How do I create a list as a key of a dictionary and add to the in different parts list?
body: <p>I have a for loop that runs through a CSV file and grabs certain elements and creates a dictionary based on two variables.</p>
  <p>Code:</p>
  <pre><code>for ind, row in sf1.iterrows():
      sf1_date = row['datekey']
      sf1_ticker = row['ticker']
      company_date[sf1_ticker] = [sf1_date]
  </code></pre>
  <p>I for example during the first iteration of the for loop, <code>sf1_ticker = 'AAPL'</code> and <code>sf1_date = '2020/03/01'</code> and the next time around, <code>sf1_ticker = 'AAPL'</code> and <code>sf1_date = '2020/06/01'</code>, how do I make the key of 'AAPL' in the dictionary equal to <code>['2020/03/01', '2020/06/01']</code></p>