擅长:python、mysql、java
<p>以下是我一直喜欢使用的一些实用函数:</p>
<pre><code>from collections import defaultdict
def group_by_key_func(iterable, key_func):
result = defaultdict(list)
for item in iterable:
result[key_func(item)].append(item)
return result
def group_by_key(iterable, key):
return group_by_key_func(iterable, lambda x: x[key])
</code></pre>
<p>有了他们,答案就变成了:</p>
<pre><code>output = {
state: {
county: [row['city'] for row in county_group]
for county, county_group in group_by_key(state_group, 'county').items()
}
for state, state_group in group_by_key(d, 'state').items()
}
</code></pre>