擅长:python、mysql、java
<p>在Python中,字典每个键只能包含一个值。但该值可以是项目的集合:</p>
<pre><code>>>> d = {'Jack London': ['Son of the Wolf', 'Chris Farrington']}
>>> d['Jack London']
['Son of the Wolf', 'Chris Farrington']
</code></pre>
<p>要从键值对序列构造这样的字典,可以执行以下操作:</p>
<pre><code>dct = {}
for author, title in items:
if author not in dct:
# Create a new entry for the author
dct[author] = [title]
else:
# Add another item to the existing entry
dct[author].append(title)
</code></pre>
<p>循环体可以变得更简洁,如下所示:</p>
<pre><code>dct = {}
for author, title in items:
dct.setdefault(author, []).append(title)
</code></pre>