Pydantic v1动态创建模型时__fields__属性未填充问题求助

问题原因 #

你使用create_model时直接将Enum类型作为字段值传入，不符合Pydantic v1的动态模型定义规则。静态类中specialty: SpecialtyEnumStatic的写法是隐式声明了必填字段，但动态创建时需要显式用**(类型, 必填标记)**或Field对象的形式定义字段，才能让Pydantic正确生成__fields__元数据。

修复后的代码 #

from enum import Enum
from langchain.pydantic_v1 import BaseModel, create_model


class SpecialtyEnumStatic(str, Enum):
    psychiatry = "SPECIALTY:Psychiatry"
    sports_medicine_internal_medicine = "SPECIALTY:Sports Medicine (Internal Medicine)"


class ProviderSearchInputStatic(BaseModel):
    specialty: SpecialtyEnumStatic


print(ProviderSearchInputStatic.__fields__)
# {'specialty': ModelField(name='specialty', type=SpecialtyEnumStatic, required=True)}

specialties = {
    'psychiatry': 'SPECIALTY:Psychiatry',
    'sports_medicine_internal_medicine': 'SPECIALTY:Sports Medicine (Internal Medicine)'
}

SpecialtyEnumDynamic = Enum('SpecialtyEnumDynamic', specialties)

# 关键修改：将字段定义改为 (类型, ...) 显式标记必填
ProviderSearchInputDynamic = create_model(
    'ProviderSearchInputDynamic',
    specialty=(SpecialtyEnumDynamic, ...),
    __base__=BaseModel
)

print(ProviderSearchInputDynamic.__fields__)
# {'specialty': ModelField(name='specialty', type=SpecialtyEnumDynamic, required=True)}

补充说明 #

• 若需要定义可选字段，可将...替换为默认值，例如specialty=(SpecialtyEnumDynamic, None)
• 也可以用Field类实现更精细化的字段控制，比如添加描述：

  from langchain.pydantic_v1 import Field
  ProviderSearchInputDynamic = create_model(
      'ProviderSearchInputDynamic',
      specialty=(SpecialtyEnumDynamic, Field(description="医生专业领域")),
      __base__=BaseModel
  )
  

内容的提问来源于stack exchange，提问作者David Stocker