请注意,这类似于 How to get @property methods in asdict? .
我有一个(卡住的)嵌套数据结构,如下所示。定义了一些(纯粹)依赖于字段的属性。
import copy
import dataclasses
import json
from dataclasses import dataclass
@dataclass(frozen=True)
class Bar:
x: int
y: int
@property
def z(self):
return self.x + self.y
@dataclass(frozen=True)
class Foo:
a: int
b: Bar
@property
def c(self):
return self.a + self.b.x - self.b.y
我可以将数据结构序列化如下:class CustomEncoder(json.JSONEncoder):
def default(self, o):
if dataclasses and dataclasses.is_dataclass(o):
return dataclasses.asdict(o)
return json.JSONEncoder.default(self, o)
foo = Foo(1, Bar(2,3))
print(json.dumps(foo, cls=CustomEncoder))
# Outputs {"a": 1, "b": {"x": 2, "y": 3}}
但是,我还想序列化属性( @property
)。注意我不想使用 __post_init__
将属性转换为字段。因为我想保持数据类的卡住。 I do not want to use obj.__setattr__
to work around the frozen fields.我也不想预先计算类外属性的值并将它们作为字段传递。我正在使用的当前解决方案是明确写出每个对象的序列化方式,如下所示:
class CustomEncoder2(json.JSONEncoder):
def default(self, o):
if isinstance(o, Foo):
return {
"a": o.a,
"b": o.b,
"c": o.c
}
elif isinstance(o, Bar):
return {
"x": o.x,
"y": o.y,
"z": o.z
}
return json.JSONEncoder.default(self, o)
foo = Foo(1, Bar(2,3))
print(json.dumps(foo, cls=CustomEncoder2))
# Outputs {"a": 1, "b": {"x": 2, "y": 3, "z": 5}, "c": 0} as desired
对于几级嵌套,这是可以管理的,但我希望有一个更通用的解决方案。例如,这是一个(hacky)解决方案,它对数据类库中的 _asdict_inner 实现进行猴子补丁。def custom_asdict_inner(obj, dict_factory):
if dataclasses._is_dataclass_instance(obj):
result = []
for f in dataclasses.fields(obj):
value = custom_asdict_inner(getattr(obj, f.name), dict_factory)
result.append((f.name, value))
# Inject this one-line change
result += [(prop, custom_asdict_inner(getattr(obj, prop), dict_factory)) for prop in dir(obj) if not prop.startswith('__')]
return dict_factory(result)
elif isinstance(obj, tuple) and hasattr(obj, '_fields'):
return type(obj)(*[custom_asdict_inner(v, dict_factory) for v in obj])
elif isinstance(obj, (list, tuple)):
return type(obj)(custom_asdict_inner(v, dict_factory) for v in obj)
elif isinstance(obj, dict):
return type(obj)((custom_asdict_inner(k, dict_factory),
custom_asdict_inner(v, dict_factory))
for k, v in obj.items())
else:
return copy.deepcopy(obj)
dataclasses._asdict_inner = custom_asdict_inner
class CustomEncoder3(json.JSONEncoder):
def default(self, o):
if dataclasses and dataclasses.is_dataclass(o):
return dataclasses.asdict(o)
return json.JSONEncoder.default(self, o)
foo = Foo(1, Bar(2,3))
print(json.dumps(foo, cls=CustomEncoder3))
# Outputs {"a": 1, "b": {"x": 2, "y": 3, "z": 5}, "c": 0} as desired
有没有推荐的方法来实现我想要做的事情?
最佳答案
这似乎与方便的 dataclass
相矛盾特征:
Class(**asdict(obj)) == obj # only for classes w/o nested dataclass attrs
如果你没有找到任何相关的 pypi 包,你总是可以像这样添加一个 2-liner:from dataclasses import asdict as std_asdict
def asdict(obj):
return {**std_asdict(obj),
**{a: getattr(obj, a) for a in getattr(obj, '__add_to_dict__', [])}}
然后,您可以在 dicts 中以自定义但简短的方式指定您想要的内容:@dataclass
class A:
f: str
__add_to_dict__ = ['f2']
@property
def f2(self):
return self.f + '2'
@dataclass
class B:
f: str
print(asdict(A('f')))
print(asdict(B('f')))
:{'f2': 'f2', 'f': 'f'}
{'f': 'f'}
关于python - 在 asdict 或序列化的数据类中包含属性的推荐方法是什么?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/64777931/