解决 FastApi 响应体中 datetime 时间格式化问题 ISO 8601: "T"

现象描述

当 FastApi 访问数据库或其他遇到 datetima 时间场景时，若直接返回响应结果，时间会被自动格式为："2024-01-01T09:30:14",而不是 "2024-01-01 09:30:14"

本文包含2种处理方法，分别对应2种响应模型，解决办法，看这里 解决方法

第1种，直接响应 pydantic 模型

代码如下

SQLAlchemy 模型

"""
@ File        : test_model.py
@ Author      : yqbao
@ Version     : V1.0.0
"""
import time
from sqlalchemy import Column, Integer, String, DateTime, Enum, SmallInteger
from db import Base


class TestTable(Base):
    __tablename__ = 'test_table'
    id = Column(Integer, primary_key=True, autoincrement=True, nullable=False)
    name = Column(String(10), nullable=False, comment='名称')
    createTime: str = Column(DateTime, nullable=False, default=time.strftime("%Y-%m-%d %H:%M:%S", time.localtime()))
    deleted = Column(Enum('0', '1'), nullable=False, server_default='0')

pydantic 模型

"""
@ File        : test_schemas.py
@ Author      : yqbao
@ Version     : V1.0.0
"""
from datetime import datetime
from typing import Union
from pydantic import BaseModel, ConfigDict


class TestTable(BaseModel):
    name: str
    createTime: datetime
    # from_attributes 将告诉 Pydantic 模型读取数据，即它不是一个 dict，而是一个 ORM 模型
    # https://docs.pydantic.dev/2.0/usage/models/#arbitrary-class-instances
    model_config = ConfigDict(
        from_attributes=True
    )

数据交互动作

"""
@ File        : test_crud.py
@ Author      : yqbao
@ Version     : V1.0.0
"""
from sqlalchemy.orm import Session
from sqlalchemy.sql import and_
from test import test_model


class TestTableCRUD(object):

    @staticmethod
    def get_test_tables(db: Session, skip: int = 0, limit: int = 100):
        """项目列表"""
        test_tables = db.query(test_model.TestTable).filter(
            test_model.TestTable.deleted == '0').offset(skip).limit(limit).all()
        return test_tables

    @staticmethod
    def get_test_table(db: Session, test_table_id: int):
        """ID查询"""
        test_table = db.query(test_model.TestTable).filter(
            and_(test_model.TestTable.id == test_table_id, test_model.TestTable.deleted == '0')).first()
        return test_table

添加路由

"""
@ File        : test_table.py
@ Author      : yqbao
@ Version     : V1.0.0
"""

from fastapi import APIRouter, Depends
from sqlalchemy.orm import Session

from db import get_db
from test import test_schemas, test_crud

router = APIRouter(
    prefix="/test-table",
    tags=["test-table"],
    responses={404: {"message": "Not Found"}}
)

crud = test_crud.TestTableCRUD()

# 注意此处的相应模型为：response_model=list[test_schemas.TestTable]
# 直接响应 pydantic 模型
@router.get("/list", response_model=list[test_schemas.TestTable], tags=["test-table"])
async def read_test_tables(skip: int = 0, limit: int = 20, db: Session = Depends(get_db)):
    db_test_tables = crud.get_test_tables(db, skip=skip, limit=limit)
    return db_test_tables


@router.get("/{test_table_id}", response_model=test_schemas.TestTable, tags=["test-table"])
async def read_test_table(test_table_id: int, db: Session = Depends(get_db)):
    db_test_table = crud.get_test_table(db, test_table_id)
    return db_test_table

其余代码省略，然后启动服务并访问/docs文档，得到如下2个路由

访问：/test-table/list?skip=0&limit=20 得到的响应体如下:

第2种，响应自定义公共模型

代码如下（仅展示与第1种不相同的代码）

pydantic 模型

"""
@ File        : test_schemas.py
@ Author      : yqbao
@ Version     : V1.0.0
@ Description : 创建初始 Pydantic模型,用于关联ORM
"""
from datetime import datetime
from typing import Union
from pydantic import BaseModel, ConfigDict

# 添加公共响应模型
class ResponseBase(BaseModel):
    code: int
    message: str
    data: Union[list, dict, str] = []

自定义响应

"""
@ File        : response.py
@ Author      : yqbao
@ Version     : V1.0.0
@ Description :
"""
from typing import Union

from fastapi.responses import JSONResponse
from fastapi import status


# 200
def response200(data: Union[list, dict, str], message: str = 'Success') -> JSONResponse:
    return JSONResponse(
        status_code=status.HTTP_200_OK,
        content={
            'code': 0,
            'message': message,
            'data': data
        }
    )


# 500
def response500(data: str = '', message: str = 'Internal Server Error') -> JSONResponse:
    return JSONResponse(
        status_code=status.HTTP_500_INTERNAL_SERVER_ERROR_CODE,
        content={
            'code': 1,
            'message': message,
            'data': data
        }
    )

路由

"""
@ File        : test_table.py
@ Author      : yqbao
@ Version     : V1.0.0
@ Description :
"""
from fastapi import APIRouter, Depends
from fastapi.encoders import jsonable_encoder
from sqlalchemy.orm import Session

from db import get_db
from extension import response
from test import test_schemas, test_crud

router = APIRouter(
    prefix="/test-table",
    tags=["test-table"],
    responses={404: {"message": "Not Found"}}
)

crud = test_crud.TestTableCRUD()

# 响应模型切换为公共响应：response_model=test_schemas.ResponseBase
@router.get("/list", response_model=test_schemas.ResponseBase, tags=["test-table"])
async def read_test_tables(skip: int = 0, limit: int = 20, db: Session = Depends(get_db)):
    db_test_tables = crud.get_test_tables(db, skip=skip, limit=limit)
    # 使用 FastApi 提供的json编码器，并交由自定义响应来返回
    db_test_tables = jsonable_encoder(db_test_tables)
    return response.response200(data=db_test_tables)


@router.get("/{test_table_id}", response_model=test_schemas.ResponseBase, tags=["test-table"])
async def read_test_table(test_table_id: int, db: Session = Depends(get_db)):
    db_test_table = crud.get_test_table(db, test_table_id)
    db_test_table = jsonable_encoder(db_test_table)
    return response.response200(data=db_test_table)

访问：/test-table/list?skip=0&limit=20 得到的响应体如下:

定位问题

时间会被自动格式为："2024-01-01T09:30:14"，这是由 Pydantic 所决定的，详见：Datetimes

解决办法

第1种，直接响应 pydantic 模型

修改代码如下

pydantic 模型

"""
@ File        : test_schemas.py
@ Author      : yqbao
@ Version     : V1.0.0
@ Description : 创建初始 Pydantic模型,用于关联ORM
"""
from datetime import datetime
from typing import Union
from pydantic import BaseModel, ConfigDict


class TestTable(BaseModel):
    name: str
    createTime: datetime
    # from_attributes 将告诉 Pydantic 模型读取数据，即它不是一个 dict，而是一个 ORM 模型
    # https://docs.pydantic.dev/2.0/usage/models/#arbitrary-class-instances
    # 添加自定义 json 编码器来重新格式化时间
    model_config = ConfigDict(
        from_attributes=True,
        json_encoders={datetime: lambda dt: dt.strftime("%Y-%m-%d %H:%M:%S")}
    )

重新访问：/test-table/list?skip=0&limit=20 得到的响应体如下:

第2种，响应自定义公共模型

修改代码如下：

路由

"""
@ File        : test_table.py
@ Author      : yqbao
@ Version     : V1.0.0
@ Description :
"""
from datetime import datetime

from fastapi import APIRouter, Depends
from fastapi.encoders import jsonable_encoder
from sqlalchemy.orm import Session

from db import get_db
from extension import response
from test import test_schemas, test_crud

router = APIRouter(
    prefix="/test-table",
    tags=["test-table"],
    responses={404: {"message": "Not Found"}}
)

crud = test_crud.TestTableCRUD()
# 添加自定义编码器
custom_encoder = {datetime: lambda dt: dt.strftime("%Y-%m-%d %H:%M:%S")}

# 响应模型切换为公共响应：response_model=test_schemas.ResponseBase
@router.get("/list", response_model=test_schemas.ResponseBase, tags=["test-table"])
async def read_test_tables(skip: int = 0, limit: int = 20, db: Session = Depends(get_db)):
    db_test_tables = crud.get_test_tables(db, skip=skip, limit=limit)
    # 使用 FastApi 提供的json 编码器，并交由自定义响应来返回
    # 添加自定义 json 编码器来重新格式化
    db_test_tables = jsonable_encoder(db_test_tables, custom_encoder=custom_encoder)
    return response.response200(data=db_test_tables)


@router.get("/{test_table_id}", response_model=test_schemas.ResponseBase, tags=["test-table"])
async def read_test_table(test_table_id: int, db: Session = Depends(get_db)):
    db_test_table = crud.get_test_table(db, test_table_id)
    db_test_table = jsonable_encoder(db_test_table, custom_encoder=custom_encoder)
    return response.response200(data=db_test_table)

重新访问：/test-table/list?skip=0&limit=20 得到的响应体如下:

本文章的原文地址
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