sqlalchemy Annotated自定义Mapped类型_sqlalchemy mapped[datetime]

 Annotated 和 Mapped，这是 SQLAlchemy 2.0 引入的新特性，允许您使用 Python 类型注解来定义模型。

from typing import Annotated
 
from sqlalchemy.orm import Mapped
from sqlalchemy.orm import mapped_column
from sqlalchemy.orm import registry
 
# typing tools will ignore init=False here
 
intpk = Annotated[int, mapped_column(init=False, primary_key=True)]
 
str50 = Annotated[str,mapped_column(String(50),nullable=True)]
 
#定义创建时间字段,新增数据自动生成创建时间,与djingo models.DateField(auto_now_add=True)功能相同
#default 和 default_factory：用于设置列的默认值。
 
datetime_create = Annotated[DateTime,mapped_column(DateTime,nullable=False,default=datetime.now)]
 
user_pk_id = Annotated[int ,mapped_column(ForeignKey('users.id'))]
 
reg = registry()
 
 
@reg.mapped_as_dataclass
class User:
    __tablename__ = "user_account"
    id: Mapped[intpk]
    user_name :Mapped[str50]
    create_time :Mapped[datetime_create]
 
 
@reg.mapped_as_dataclass
class Userinfo:
    __tablename__ = "user_account"
    id: Mapped[intpk]
    user_pk :Mapped[user_pk_id]
    create_time :Mapped[datetime_create]
 
 
@reg.mapped_as_dataclass
class Userinfo:
    __tablename__ = "user_account"
    id: Mapped[intpk]
    user_pk :Mapped[user_pk_id]
    create_time :Mapped[datetime_create]
 
 
# typing error: Argument missing for parameter "id"
u1 = User()

from decimal import Decimal
 
from typing_extensions import Annotated
 
from sqlalchemy import Numeric
from sqlalchemy import String
from sqlalchemy.orm import DeclarativeBase
from sqlalchemy.orm import Mapped
from sqlalchemy.orm import mapped_column
from sqlalchemy.orm import registry
 
str_30 = Annotated[str, 30]
str_50 = Annotated[str, 50]
num_12_4 = Annotated[Decimal, 12]
num_6_2 = Annotated[Decimal, 6]
 
 
class Base(DeclarativeBase):
    registry = registry(
        type_annotation_map={
            str_30: String(30),
            str_50: String(50),
            num_12_4: Numeric(12, 4),
            num_6_2: Numeric(6, 2),
        }
    )