擅长:python、mysql、java
<p>您可以使用<code>defaultdict</code>。你知道吗</p>
<pre><code>In [1]: from collections import defaultdict
In [2]: student = defaultdict(lambda: 'Senior')
In [3]: for k, v in ((1, 'Freshman'), (2, 'Sophmore'), (3, 'Junior')):
...: student[k] = v
...:
In [4]: student[1]
Out[4]: 'Freshman'
In [5]: student[2]
Out[5]: 'Sophmore'
In [6]: student[3]
Out[6]: 'Junior'
In [7]: student[4]
Out[7]: 'Senior'
In [8]: student[9]
Out[8]: 'Senior'
</code></pre>