嵌套字典到具有默认值的对象

Question

我正在使用dataclasses + dataclasses_json来实现我的web。

我的应用程序会将请求从dict解码到object，我希望object仍然可以在没有填充每个字段的情况下生成，并用默认值填充空字段。

这是我可能的代码：

from dataclasses import dataclass
from dataclasses_json import dataclass_json

@dataclass
class Glasses:
    color: str
    size: str
    prize: int

@dataclass
class Tshirt:
    color: str
    size: str
    prize: int

@dataclass_json
@dataclass
class People:
    Name : str = 'James'
    Age : int = 25
    Glasses: Glasses = Glasses('black', 'M', 2500)
    Tshirt: Tshirt = Tshirt('black', 'XL', 500)

p = {
    'Name': 'Gino',
    'Age': 20,
    'Glasses': {
        'color' : 'red',
        'size' : 'M',
        'prize' : 4000
    },
    'Tshirt': {
        'color' : 'red',
        'size' : 'M',
        'prize' : 4000
    }
}

a = People.from_dict(p)
print(a)

然后我会得到错误

Traceback (most recent call last):
  File ".\People.py", line 39, in <module>
    a = People.from_dict(p)
  File "C:\Python3.7\lib\site-packages\dataclasses_json\api.py", line 83, in from_dict
    return _decode_dataclass(cls, kvs, infer_missing)
  File "C:\Python3.7\lib\site-packages\dataclasses_json\core.py", line 133, in _decode_dataclass
    overrides = _user_overrides_or_exts(cls)
  File "C:\Python3.7\lib\site-packages\dataclasses_json\core.py", line 59, in _user_overrides_or_exts
    if field.type in encoders:
TypeError: unhashable type: 'Glasses'

我发现我可以添加(eq=True，frozen=True)，所以我将代码更改为

from dataclasses import dataclass
from dataclasses_json import dataclass_json

@dataclass(eq=True, frozen=True)
class Glasses:
    color: str
    size: str
    prize: int

@dataclass(eq=True, frozen=True)
class Tshirt:
    color: str
    size: str
    prize: int

@dataclass_json
@dataclass
class People:
    Name : str = 'James'
    Age : int = 25
    Glasses: Glasses = Glasses('black', 'M', 2500)
    Tshirt: Tshirt = Tshirt('black', 'XL', 500)

p = {
    'Name': 'Gino',
    'Age': 20,
    'Glasses': {
        'color' : 'red',
        'size' : 'M',
        'prize' : 4000
    },
    'Tshirt': {
        'color' : 'red',
        'size' : 'M',
        'prize' : 4000
    }
}

a = People.from_dict(p)
print(a)

我得到了另一个错误

  File ".\People.py", line 39, in <module>
    a = People.from_dict(p)
  File "C:\Python3.7\lib\site-packages\dataclasses_json\api.py", line 83, in from_dict
    return _decode_dataclass(cls, kvs, infer_missing)
  File "C:\Python3.7\lib\site-packages\dataclasses_json\core.py", line 198, in _decode_dataclass
    infer_missing)
  File "C:\Python3.7\lib\site-packages\dataclasses_json\core.py", line 131, in _decode_dataclass
    if isinstance(kvs, cls):
TypeError: isinstance() arg 2 must be a type or tuple of types

有没有可能在不自己编码的情况下使用内置函数来满足我的需求？

Answer 1

您有字段名称和类型名称冲突。为了让你的代码工作，你必须有不同于类名的JSON字段命名，即你不能有字段"Glasses"和类Glasses，你必须将类重命名为Glasses_或者重命名你的字段名。

另一种选择是为类类型创建别名，即为Glasses创建别名GlassesT。

具有类型别名的代码版本：

Try it online!

from dataclasses import dataclass
from dataclasses_json import dataclass_json

@dataclass
class Glasses:
    color: str
    size: str
    prize: int

GlassesT = Glasses

@dataclass
class Tshirt:
    color: str
    size: str
    prize: int
    
TshirtT = Tshirt
    
@dataclass_json
@dataclass
class People:
    Name : str = 'James'
    Age : int = 25
    Glasses: GlassesT = GlassesT('black', 'M', 2500)
    Tshirt: TshirtT = TshirtT('black', 'XL', 500)

p = {
    'Name': 'Gino',
    'Age': 20,
    'Glasses': {
        'color' : 'red',
        'size' : 'M',
        'prize' : 4000
    },
    'Tshirt': {
        'color' : 'red',
        'size' : 'M',
        'prize' : 4000
    }
}

a = People.from_dict(p)
print(a)

输出：

People(Name='Gino', Age=20, Glasses=Glasses(color='red', size='M', prize=4000), Tshirt=Tshirt(color='red', size='M', prize=4000))

具有重命名类的代码版本：

Try it online!

from dataclasses import dataclass
from dataclasses_json import dataclass_json

@dataclass
class Glasses_:
    color: str
    size: str
    prize: int

@dataclass
class Tshirt_:
    color: str
    size: str
    prize: int

@dataclass_json
@dataclass
class People:
    Name : str = 'James'
    Age : int = 25
    Glasses: Glasses_ = Glasses_('black', 'M', 2500)
    Tshirt: Tshirt_ = Tshirt_('black', 'XL', 500)

p = {
    'Name': 'Gino',
    'Age': 20,
    'Glasses': {
        'color' : 'red',
        'size' : 'M',
        'prize' : 4000
    },
    'Tshirt': {
        'color' : 'red',
        'size' : 'M',
        'prize' : 4000
    }
}

a = People.from_dict(p)
print(a)

输出：

People(Name='Gino', Age=20, Glasses=Glasses_(color='red', size='M', prize=4000), Tshirt=Tshirt_(color='red', size='M', prize=4000))