title: How slow is Python's string concatenation vs. str.join?
body: <p>As a result of the comments in my answer on <a href="https://stackoverflow.com/questions/3054604/iterate-over-the-lines-of-a-string/3054679#3054679">this thread</a>, I wanted to know what the speed difference is between the <code>+=</code> operator and <code>''.join()</code></p>
  
  <p>So what is the speed comparison between the two?</p>