'backwards' enumerate
<p>Is there a way to get a generator/iterator that yeilds the reverse of <code>enumerate</code>:</p>

<pre><code>from itertools import izip, count

enumerate(I) # -&gt; (indx, v)
izip(I, count()) # -&gt; (v, indx)
</code></pre>

<p>without pulling in <code>itertools</code>?</p>
