title: What is the difference between !r and %r in Python?
body: <p>As the title states, what is the difference between these two flags? It seems they both convert the value to a string using repr()?
  Also, in this line of code: </p>
  
  <pre><code>"{0!r:20}".format("Hello")  
  </code></pre>
  
  <p>What does the 0 in front of the !r do?</p>