擅长:python、mysql、java
<p>当python的<code>sort</code>是<a href="http://en.wikipedia.org/wiki/Stable_sort#Stability">stable</a>时,可以执行连续的排序循环。不过,您需要先按<em>次键</em>排序。另请参见<a href="http://docs.python.org/howto/sorting.html#sort-stability-and-complex-sorts">official HOW TO</a>。</p>
<pre><code>from operator import itemgetter
l = [['a',2], ['a',1], ['b', 2], ['a',3], ['b',1], ['b',3]]
l.sort(key=itemgetter(1))
l.sort(key=itemgetter(0), reverse=True)
# [['b', 1], ['b', 2], ['b', 3], ['a', 1], ['a', 2], ['a', 3]]
</code></pre>