title: How to pass tuple1 if ... else tuple2 to str.format?
body: <p>Put simply, why do I get the following error?</p>
  
  <pre><code>&gt;&gt;&gt; yes = True
  &gt;&gt;&gt; 'no [{0}] yes [{1}]'.format((" ", "x") if yes else ("x", " "))
  Traceback (most recent call last):
    File "&lt;stdin&gt;", line 1, in &lt;module&gt;
  IndexError: tuple index out of range
  </code></pre>
  
  <p>I use python 2.6.</p>