title: format r(repr) of print in python3
body: <pre class="lang-none prettyprint-override"><code>&gt;&gt;&gt;print('You say:{0:r}'.format("i love you"))
  Traceback (most recent call last):
    File "&lt;pyshell#5&gt;", line 1, in &lt;module&gt;
      print('You say:{0:r}'.format("i love you"))
  ValueError: Unknown format code 'r' for object of type 'str'
  </code></pre>
  
  <p>I just use <code>%r(repr())</code> in python2, and it should work in python3.5. Why is it?</p>
  
  <p>Besides, what format should I use?</p>