擅长:python、mysql、java
<p>使用<code>itertools(product and chain)</code>和<code>collections.Counter</code>的组合</p>
<pre><code>from itertools import product, chain
from collections import Counter
{' '.join(k):v for k,v in Counter(chain(*[product(i[:2],[i[-1]]) for i in dttrain])).items()}
</code></pre>
<p>输出:</p>
^{pr2}$