我如何使Python字典成员访问通过点“。”?

例如,我想写mydict.val而不是mydict['val']。

我还想以这种方式访问嵌套字典。例如

mydict.mydict2.val 

会提到

mydict = { 'mydict2': { 'val': ... } }

当前回答

如果你想pickle你修改后的字典,你需要添加几个状态方法到上面的答案:

class DotDict(dict):
    """dot.notation access to dictionary attributes"""
    def __getattr__(self, attr):
        return self.get(attr)
    __setattr__= dict.__setitem__
    __delattr__= dict.__delitem__

    def __getstate__(self):
        return self

    def __setstate__(self, state):
        self.update(state)
        self.__dict__ = self

其他回答

不是对OP问题的直接回答,但受到启发,也许对一些人有用。我已经创建了一个基于对象的解决方案使用内部__dict__(在任何方式优化代码)

payload = {
    "name": "John",
    "location": {
        "lat": 53.12312312,
        "long": 43.21345112
    },
    "numbers": [
        {
            "role": "home",
            "number": "070-12345678"
        },
        {
            "role": "office",
            "number": "070-12345679"
        }
    ]
}


class Map(object):
    """
    Dot style access to object members, access raw values
    with an underscore e.g.

    class Foo(Map):
        def foo(self):
            return self.get('foo') + 'bar'

    obj = Foo(**{'foo': 'foo'})

    obj.foo => 'foobar'
    obj._foo => 'foo'

    """

    def __init__(self, *args, **kwargs):
        for arg in args:
            if isinstance(arg, dict):
                for k, v in arg.iteritems():
                    self.__dict__[k] = v
                    self.__dict__['_' + k] = v

        if kwargs:
            for k, v in kwargs.iteritems():
                self.__dict__[k] = v
                self.__dict__['_' + k] = v

    def __getattribute__(self, attr):
        if hasattr(self, 'get_' + attr):
            return object.__getattribute__(self, 'get_' + attr)()
        else:
            return object.__getattribute__(self, attr)

    def get(self, key):
        try:
            return self.__dict__.get('get_' + key)()
        except (AttributeError, TypeError):
            return self.__dict__.get(key)

    def __repr__(self):
        return u"<{name} object>".format(
            name=self.__class__.__name__
        )


class Number(Map):
    def get_role(self):
        return self.get('role')

    def get_number(self):
        return self.get('number')


class Location(Map):
    def get_latitude(self):
        return self.get('lat') + 1

    def get_longitude(self):
        return self.get('long') + 1


class Item(Map):
    def get_name(self):
        return self.get('name') + " Doe"

    def get_location(self):
        return Location(**self.get('location'))

    def get_numbers(self):
        return [Number(**n) for n in self.get('numbers')]


# Tests

obj = Item({'foo': 'bar'}, **payload)

assert type(obj) == Item
assert obj._name == "John"
assert obj.name == "John Doe"
assert type(obj.location) == Location
assert obj.location._lat == 53.12312312
assert obj.location._long == 43.21345112
assert obj.location.latitude == 54.12312312
assert obj.location.longitude == 44.21345112

for n in obj.numbers:
    assert type(n) == Number
    if n.role == 'home':
        assert n.number == "070-12345678"
    if n.role == 'office':
        assert n.number == "070-12345679"

这是我从很久以前的一个项目里挖出来的。它可能还可以再优化一点,但就是这样了。

class DotNotation(dict):
    
    __setattr__= dict.__setitem__
    __delattr__= dict.__delitem__

    def __init__(self, data):
        if isinstance(data, str):
            data = json.loads(data)
    
        for name, value in data.items():
            setattr(self, name, self._wrap(value))

    def __getattr__(self, attr):
        def _traverse(obj, attr):
            if self._is_indexable(obj):
                try:
                    return obj[int(attr)]
                except:
                    return None
            elif isinstance(obj, dict):
                return obj.get(attr, None)
            else:
                return attr
        if '.' in attr:
            return reduce(_traverse, attr.split('.'), self)
        return self.get(attr, None)

    def _wrap(self, value):
        if self._is_indexable(value):
            # (!) recursive (!)
            return type(value)([self._wrap(v) for v in value])
        elif isinstance(value, dict):
            return DotNotation(value)
        else:
            return value
    
    @staticmethod
    def _is_indexable(obj):
        return isinstance(obj, (tuple, list, set, frozenset))


if __name__ == "__main__":
    test_dict = {
        "dimensions": {
            "length": "112",
            "width": "103",
            "height": "42"
        },
        "meta_data": [
            {
                "id": 11089769,
                "key": "imported_gallery_files",
                "value": [
                    "https://example.com/wp-content/uploads/2019/09/unnamed-3.jpg",
                    "https://example.com/wp-content/uploads/2019/09/unnamed-2.jpg",
                    "https://example.com/wp-content/uploads/2019/09/unnamed-4.jpg"
                ]
            }
        ]
    }
    dotted_dict = DotNotation(test_dict)
    print(dotted_dict.dimensions.length) # => '112'
    print(getattr(dotted_dict, 'dimensions.length')) # => '112'
    print(dotted_dict.meta_data[0].key) # => 'imported_gallery_files'
    print(getattr(dotted_dict, 'meta_data.0.key')) # => 'imported_gallery_files'
    print(dotted_dict.meta_data[0].value) # => ['link1','link2','link2']
    print(getattr(dotted_dict, 'meta_data.0.value')) # => ['link1','link2','link3']
    print(dotted_dict.meta_data[0].value[2]) # => 'link3'
    print(getattr(dotted_dict, 'meta_data.0.value.2')) # => 'link3'

如果你想pickle你修改后的字典,你需要添加几个状态方法到上面的答案:

class DotDict(dict):
    """dot.notation access to dictionary attributes"""
    def __getattr__(self, attr):
        return self.get(attr)
    __setattr__= dict.__setitem__
    __delattr__= dict.__delitem__

    def __getstate__(self):
        return self

    def __setstate__(self, state):
        self.update(state)
        self.__dict__ = self

我只需要使用虚线路径字符串访问字典,所以我想到了:

def get_value_from_path(dictionary, parts):
    """ extracts a value from a dictionary using a dotted path string """

    if type(parts) is str:
        parts = parts.split('.')

    if len(parts) > 1:
        return get_value_from_path(dictionary[parts[0]], parts[1:])

    return dictionary[parts[0]]

a = {'a':{'b':'c'}}
print(get_value_from_path(a, 'a.b')) # c

如果你已经在使用pandas,你可以构造一个pandas Series或DataFrame,从中你可以通过点语法访问项目:

1级字典:

import pandas as pd

my_dictionary = pd.Series({
  'key1': 'value1',
  'key2': 'value2'
})

print(my_dictionary.key1)
# Output: value1

2级字典:

import pandas as pd

my_dictionary = pd.DataFrame({
  'key1': {
    'inner_key1': 'value1'
  },
  'key2': {
    'inner_key2': 'value2'
  }
})

print(my_dictionary.key1.inner_key1)
# Output: value1

请注意,这可能在规范化数据结构(其中每个字典条目都具有相同的结构)下工作得更好。在上面的第二个例子中,得到的DataFrame是:

              key1    key2
inner_key1  value1     NaN
inner_key2     NaN  value2