擅长:python、mysql、java
<p>您要使用<code>defaultdict</code>:</p>
<pre><code>>>> from collections import defaultdict
>>> d = defaultdict(int)
>>> d['a'] += 1
>>> d['b'] += 1
>>> d['b'] += 1
>>> print d['a'], d['b'], d['c']
1 2 0
</code></pre>