Python: Best Way to Exchange Keys with Values in a Dictionary?

http://stackoverflow.com/questions/1031851/python-best-way-to-exchange-keys-with-values-in-a-dictionary

answer is:

<code><span class="pln">res </span><span class="pun">=</span><span class="pln"> dict</span><span class="pun">((</span><span class="pln">v</span><span class="pun">,</span><span class="pln">k</span><span class="pun">)</span><span class="pln"> </span><span class="kwd">for</span><span class="pln"> k</span><span class="pun">,</span><span class="pln">v </span><span class="kwd">in</span><span class="pln"> a</span><span class="pun">.</span><span class="pln">iteritems</span><span class="pun">())</span><span class="pln">
</span></code>

a=dict([(1,2),(2,3)])