pandas多级分组实现排序的方法

In [70]: df = pd.DataFrame(((random.randint(2012, 2016), random.choice(['tech', 'art', 'office']), '%dk-%dk'%(random.randint(2,10), random.randint(10, 20)), '') for _ in xrange(10000)), columns=['publish_time', 'classf', 'salary', 'title'])

In [71]: df.head()
Out[71]:
 publish_time classf salary title
0 2012 art 2k-19k
1 2014 office 5k-17k
2 2013 office 2k-10k
3 2013 art 5k-14k
4 2013 art 2k-14k

In [72]: df.groupby(['publish_time', 'classf', 'salary']).count()['title'].groupby(level=0, group_keys=False).nlargest(10)
Out[72]:
publish_time classf salary
2012 art 7k-13k 18
 4k-13k 16
 tech 3k-12k 14
 art 6k-16k 13
 8k-15k 13
 office 5k-18k 13
 tech 4k-14k 13