Why does Python's iter() on a mapping return iterkeys() instead of iteritems()?
<p>It seems like if you want to get the keys of a mapping, you ask for them; otherwise, give me the <em>whole</em> mapping (constituted by a set of key-value pairs). Is there a historical reason for this?</p>

<p>Check out <a href="http://mail.python.org/pipermail/python-3000/2007-September/010209.html" rel="nofollow">this thread</a> for a discussion on the reasons behind this behavior (including that Guido likes it, and it's <a href="http://mail.python.org/pipermail/python-3000/2007-September/010222.html" rel="nofollow">not likely to change</a>).</p>
