title: python data frames - splitting string column into two columns
body: <p>I'm playing with Whatsapp's history chat.
  I want to split the message column into two columns - time and message.</p>
  
  <p><a href="https://i.stack.imgur.com/2I5Cm.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/2I5Cm.png" alt="enter image description here"></a></p>
  
  <p>In order to split the two with the delimiter " - " I tried:</p>
  
  <pre><code>history['message'] = pd.DataFrame([line.split(" - ",1) for line in history['message']])
  </code></pre>
  
  <p>But history['message'] becomes the time only.</p>
  
  <p>I don't understand why, because the line.split(" - ", 1) supposes to give a list of 2 elements at most.</p>