Question

如何将dict dict中的值存储到路径？例如，我们可以轻松地将name值的路径存储在变量name_field中：

person = {}
person['name'] = 'Jeff Atwood'
person['address'] = {}
person['address']['street'] = 'Main Street'
person['address']['zip'] = '12345'
person['address']['city'] = 'Miami'

# Get name
name_field = 'name'
print( person[name_field] )

如何存储city值的路径？

# Get city
city_field = ['address', 'city']
print( person[city_field] )  // Obviously won't work!

Answer 1

你可以这样做：

path = ('address', 'city')
lookup = person
for key in path:
    lookup = lookup[key]

print lookup
# gives: Miami

如果路径的一部分不存在，这将引发KeyError。

如果path由一个值组成，例如('name',)，它也会有用。

Answer 2

您可以使用reduce功能执行此操作

print reduce(lambda x, y: x[y], city_field, person)

<强>输出

Miami

Answer 3

使用Simeon（和Unubtu删除的答案）的另一种方法是创建自己的dict类，定义一个额外的方法：

class mydict(dict):
    def lookup(self, *args):
        tmp = self
        for field in args:
            tmp = tmp[field]
        return tmp

person = mydict()
person['name'] = 'Jeff Atwood'
person['address'] = {}
person['address']['street'] = 'Main Street'
person['address']['zip'] = '12345'
person['address']['city'] = 'Miami'

print(person.lookup('address', 'city'))
print(person.lookup('name'))
print(person.lookup('city'))

导致：

Miami
Jeff Atwood
Traceback (most recent call last):
  File "look.py", line 17, in <module>
    print(person.lookup('city'))
  File "look.py", line 5, in lookup
    tmp = tmp[field]
KeyError: 'city'

您可以根据thefourtheye的建议缩短循环次数。如果你想要真正喜欢，你可以覆盖像__get__这样的私有方法，以允许像person['address', 'city']这样的情况，但事情可能会变得棘手。

Answer 4

这是另一种方式 - 与Simeon Visser的行为完全相同

from operator import itemgetter
pget = lambda map, path: reduce(lambda x,p: itemgetter(p)(x), path, map)

使用您的示例数据：

person = {
  'name': 'Jeff Atwood',
  'address': {
    'street': 'Main Street',
    'zip': '12345',
    'city': 'Miami',
  },
}

pget(person, ('address', 'zip')) # Prints '12345'
pget(person, ('name',))          # Prints 'Jeff Atwood'
pget(person, ('nope',))          # Raises KeyError

存储字典值的路径

4 个答案: