build list of lists using comprehension lists two at a time
<p>I am using the following code to build a list of lists:</p>

<pre><code>res = []
for i in I:
   res.append(x)
   res.append(y[i])
</code></pre>

<p>so my final list is <code>[x, y[0], x, y[1],...]</code> where <code>x</code> and <code>y[i]</code> are also lists.</p>

<p>Is there a way building this list using list comprehensions, instead of for loop?</p>
