python - 字典列表 - 如何读取字典中的特定值

Question

我有一个清单

lis = [{'score': 12, 'name': 'random_content', 'numrep': 11}, {'score': 31, 'name': 'some_content', 'numrep': 10}]

如何读取此列表中特定键的值？即名称的分值：上面列表中的“some_content”，等于 31。

Answer 1

最好在dict此处使用 a 来快速查找任何'name'：

from collections import defaultdict
lis = [{'score': 12, 'name': 'random_content', 'numrep': 11}, {'score': 31, 'name': 'some_content', 'numrep': 10}]
dic = defaultdict(dict)
for d in lis:
    for k,v in ((k,v) for k,v in d.iteritems() if k != 'name'):
        dic[d['name']][k] = v

现在dic看起来像：

defaultdict(<type 'dict'>,
{'random_content': {'score': 12, 'numrep': 11},
 'some_content': {'score': 31, 'numrep': 10}
})

及时获取'some_content'分数O(1)：

>>> dic['some_content']['score']
31

Answer 2

使用列表综合，生成器表达式：

>>> [x for x in lis if x['name'] == 'some_content']
[{'score': 31, 'name': 'some_content', 'numrep': 10}]
>>> [x['score'] for x in lis if x['name'] == 'some_content']
[31]
>>> next(x['score'] for x in lis if x['name'] == 'some_content')
31

>>> next(x['score'] for x in lis if x['name'] == 'ome_content')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
StopIteration
>>> next((x['score'] for x in lis if x['name'] == 'no-such-content'), 'fallback')
'fallback'