擅长:python、mysql、java
<p>使用<a href="https://docs.python.org/3/library/collections.html#collections.Counter" rel="nofollow noreferrer">^{<cd1>}</a>与<a href="https://docs.python.org/3/tutorial/classes.html#generator-expressions" rel="nofollow noreferrer">generator expression</a>组合,可以获得项目计数:</p>
<pre><code>>>> a = [["b", "a", 3], ["a", "b", 4], ["y", "a", 2], ["b", "a", "b"]]
>>> from collections import Counter
>>> Counter(item[1] for item in a) # gen-expr to yields 2nd ([1]) items
Counter({'a': 3, 'b': 1})
</code></pre>
<p>要以序列列表的形式获取结果,请执行以下操作:</p>
<pre><code>>>> Counter(item[1] for item in a).most_common()
[('a', 3), ('b', 1)]
>>> [list(x) for x in Counter(item[1] for item in a).most_common()]
[['a', 3], ['b', 1]]
</code></pre>