将dict列表转换为更便于下拉的形式

Question

我试图创建一个友好的格式为多个相关的HTML下拉列表。你知道吗

如何转换字典d使其看起来像字典output？你知道吗

d = [
    {"state": "California", "county": "Monterey", "city": "Salinas"},
    {"state": "California", "county": "Monterey", "city": "Gonzales"},
    {"state": "Oregon", "county": "Douglas", "city": "Roseburg"},
    {"state": "Oregon", "county": "Douglas", "city": "Winston"},
    {"state": "California", "county": "Alameda", "city": "Berkeley"},
]

output = {
    "California": {
        "Monterey": ["Salinas", "Gonzales"],
        "Alameda": ["Berkeley"],
    },
    "Oregon": {
        "Douglas": ["Roseburg", "Winston"],
    }
}

我不希望使用Pandas，只使用纯Python，因为我还需要将解决方案转换为JavaScript（尽管如此，我尝试过将d转换为数据帧，应用各种方向，但没有一个方向提供我想要的输出）。你知道吗

Answer 1

循环浏览列表并处理每个字典，将每个条目添加到输出中的适当位置，必要时创建新的字典和列表。你知道吗

d = [
    {"state": "California", "county": "Monterey", "city": "Salinas"},
    {"state": "California", "county": "Monterey", "city": "Gonzales"},
    {"state": "Oregon", "county": "Douglas", "city": "Roseburg"},
    {"state": "Oregon", "county": "Douglas", "city": "Winston"},
    {"state": "California", "county": "Alameda", "city": "Berkeley"},
]

output = {}

for place in d:
    if place['state'] not in output:
        output[place['state']] = {}
    if place['county'] not in output[place['state']]:
        output[place['state']][place['county']] = []
    output[place['state']][place['county']].append(place['city'])

结果：

>>> import pprint
>>> pprint.pprint(output, width=30)
{'California': {'Alameda': ['Berkeley'],
                'Monterey': ['Salinas',
                             'Gonzales']},
 'Oregon': {'Douglas': ['Roseburg',
                        'Winston']}}

或者，用collections.defaultdict：

from collections import defaultdict as dd
output = dd(lambda: dd(list))
for place in d:
    output[place['state']][place['county']].append(place['city'])

结果是：

>>> pprint.pprint(output)
defaultdict(<function <lambda> at 0x000000E254B53E18>,
            {'California': defaultdict(<class 'list'>,
                                       {'Alameda': ['Berkeley'],
                                        'Monterey': ['Salinas', 'Gonzales']}),
             'Oregon': defaultdict(<class 'list'>,
                                   {'Douglas': ['Roseburg', 'Winston']})})