title: How to add lists of varying lengths as rows to a DataFrame
body: <p>I have oodles of lists that I need to combine into a DataFrame, each as a row. The lists are varying lengths. The column names will just be index numbers but I don't know how to dynamically generate them as needed.</p>
  <pre><code>l1 = [1,2,3]
  l2 = [10,22,13,4]
  l3 = [2]
  df = pd.DataFrame()
  df.loc[len(df)] = pd.DataFrame(l1, columns=list(range(len(l1))))
  </code></pre>
  <p>I get this error: ValueError: Shape of passed values is (3, 1), indices imply (3, 3)</p>