title: How to create a pandas dataframe with rows of python list data?
body: <p>I would like to initialize a <code>pandas dataframe</code> with column titles and one row of data. I would then like to append rows of data onto the end of this <code>dataframe</code> as I iterate through a file that I am reading the data from.</p>
  <p>Here is an example of what I am doing and the issue that I am running into:</p>
  <pre><code>titles = ['a','b','c','d']
  data = ['1','2','3','4']
  df = pd.DataFrame(data, columns=titles)
  
  ValueError: Shape of passed values is (4, 1), indices imply (4, 4)
  </code></pre>
  <p>I know that this is because the data is being inserted as one column instead of one row. How can I make sure the data is inserted as a row?</p>
  <p>What is the best way to append additional rows of data onto the end of this <code>dataframe</code>?</p>