使用 FastAPI 读取单个模型

现在，我们为 FastAPI 应用程序添加一个路径操作，以读取单个模型。

单个英雄的路径操作

我们来添加一个新的路径操作，以读取单个英雄。

我们希望根据 id 获取英雄，因此我们将使用一个路径参数 hero_id。

信息

如果您需要回顾路径参数的工作原理，包括其数据验证，请查看 FastAPI 关于路径参数的文档。

Python 3.10+

from fastapi import FastAPI, HTTPException
from sqlmodel import Field, Session, SQLModel, create_engine, select

# Code here omitted 👈

@app.get("/heroes/{hero_id}", response_model=HeroPublic)
def read_hero(hero_id: int):
    with Session(engine) as session:
        hero = session.get(Hero, hero_id)
        if not hero:
            raise HTTPException(status_code=404, detail="Hero not found")
        return hero

👀 完整文件预览

Python 3.10+

from fastapi import FastAPI, HTTPException
from sqlmodel import Field, Session, SQLModel, create_engine, select


class HeroBase(SQLModel):
    name: str = Field(index=True)
    secret_name: str
    age: int | None = Field(default=None, index=True)


class Hero(HeroBase, table=True):
    id: int | None = Field(default=None, primary_key=True)


class HeroCreate(HeroBase):
    pass


class HeroPublic(HeroBase):
    id: int


sqlite_file_name = "database.db"
sqlite_url = f"sqlite:///{sqlite_file_name}"

connect_args = {"check_same_thread": False}
engine = create_engine(sqlite_url, echo=True, connect_args=connect_args)


def create_db_and_tables():
    SQLModel.metadata.create_all(engine)


app = FastAPI()


@app.on_event("startup")
def on_startup():
    create_db_and_tables()


@app.post("/heroes/", response_model=HeroPublic)
def create_hero(hero: HeroCreate):
    with Session(engine) as session:
        db_hero = Hero.model_validate(hero)
        session.add(db_hero)
        session.commit()
        session.refresh(db_hero)
        return db_hero


@app.get("/heroes/", response_model=list[HeroPublic])
def read_heroes():
    with Session(engine) as session:
        heroes = session.exec(select(Hero)).all()
        return heroes


@app.get("/heroes/{hero_id}", response_model=HeroPublic)
def read_hero(hero_id: int):
    with Session(engine) as session:
        hero = session.get(Hero, hero_id)
        if not hero:
            raise HTTPException(status_code=404, detail="Hero not found")
        return hero

🤓 其他版本和变体

Python 3.9+Python 3.8+

from typing import Optional

from fastapi import FastAPI, HTTPException
from sqlmodel import Field, Session, SQLModel, create_engine, select


class HeroBase(SQLModel):
    name: str = Field(index=True)
    secret_name: str
    age: Optional[int] = Field(default=None, index=True)


class Hero(HeroBase, table=True):
    id: Optional[int] = Field(default=None, primary_key=True)


class HeroCreate(HeroBase):
    pass


class HeroPublic(HeroBase):
    id: int


sqlite_file_name = "database.db"
sqlite_url = f"sqlite:///{sqlite_file_name}"

connect_args = {"check_same_thread": False}
engine = create_engine(sqlite_url, echo=True, connect_args=connect_args)


def create_db_and_tables():
    SQLModel.metadata.create_all(engine)


app = FastAPI()


@app.on_event("startup")
def on_startup():
    create_db_and_tables()


@app.post("/heroes/", response_model=HeroPublic)
def create_hero(hero: HeroCreate):
    with Session(engine) as session:
        db_hero = Hero.model_validate(hero)
        session.add(db_hero)
        session.commit()
        session.refresh(db_hero)
        return db_hero


@app.get("/heroes/", response_model=list[HeroPublic])
def read_heroes():
    with Session(engine) as session:
        heroes = session.exec(select(Hero)).all()
        return heroes


@app.get("/heroes/{hero_id}", response_model=HeroPublic)
def read_hero(hero_id: int):
    with Session(engine) as session:
        hero = session.get(Hero, hero_id)
        if not hero:
            raise HTTPException(status_code=404, detail="Hero not found")
        return hero

from typing import List, Optional

from fastapi import FastAPI, HTTPException
from sqlmodel import Field, Session, SQLModel, create_engine, select


class HeroBase(SQLModel):
    name: str = Field(index=True)
    secret_name: str
    age: Optional[int] = Field(default=None, index=True)


class Hero(HeroBase, table=True):
    id: Optional[int] = Field(default=None, primary_key=True)


class HeroCreate(HeroBase):
    pass


class HeroPublic(HeroBase):
    id: int


sqlite_file_name = "database.db"
sqlite_url = f"sqlite:///{sqlite_file_name}"

connect_args = {"check_same_thread": False}
engine = create_engine(sqlite_url, echo=True, connect_args=connect_args)


def create_db_and_tables():
    SQLModel.metadata.create_all(engine)


app = FastAPI()


@app.on_event("startup")
def on_startup():
    create_db_and_tables()


@app.post("/heroes/", response_model=HeroPublic)
def create_hero(hero: HeroCreate):
    with Session(engine) as session:
        db_hero = Hero.model_validate(hero)
        session.add(db_hero)
        session.commit()
        session.refresh(db_hero)
        return db_hero


@app.get("/heroes/", response_model=List[HeroPublic])
def read_heroes():
    with Session(engine) as session:
        heroes = session.exec(select(Hero)).all()
        return heroes


@app.get("/heroes/{hero_id}", response_model=HeroPublic)
def read_hero(hero_id: int):
    with Session(engine) as session:
        hero = session.get(Hero, hero_id)
        if not hero:
            raise HTTPException(status_code=404, detail="Hero not found")
        return hero

例如，要获取 ID 为 2 的英雄，我们将向以下地址发送 GET 请求：

/heroes/2

错误处理

然后，因为 FastAPI 已经确保 hero_id 是一个实际的整数，我们可以直接将其与 Hero.get() 一起使用，尝试通过该 ID 获取一个英雄。

但是，如果该整数不是数据库中任何英雄的 ID，它将找不到任何内容，并且变量 hero 将为 None。

因此，我们在一个 if 块中检查它，如果它是 None，我们就引发一个带有 404 状态码的 HTTPException。

要使用它，我们首先从 fastapi 导入 HTTPException。

这将让客户端知道他们可能犯了错误，请求了一个数据库中不存在的英雄。

Python 3.10+

from fastapi import FastAPI, HTTPException
from sqlmodel import Field, Session, SQLModel, create_engine, select

# Code here omitted 👈

@app.get("/heroes/{hero_id}", response_model=HeroPublic)
def read_hero(hero_id: int):
    with Session(engine) as session:
        hero = session.get(Hero, hero_id)
        if not hero:
            raise HTTPException(status_code=404, detail="Hero not found")
        return hero

👀 完整文件预览

Python 3.10+

from fastapi import FastAPI, HTTPException
from sqlmodel import Field, Session, SQLModel, create_engine, select


class HeroBase(SQLModel):
    name: str = Field(index=True)
    secret_name: str
    age: int | None = Field(default=None, index=True)


class Hero(HeroBase, table=True):
    id: int | None = Field(default=None, primary_key=True)


class HeroCreate(HeroBase):
    pass


class HeroPublic(HeroBase):
    id: int


sqlite_file_name = "database.db"
sqlite_url = f"sqlite:///{sqlite_file_name}"

connect_args = {"check_same_thread": False}
engine = create_engine(sqlite_url, echo=True, connect_args=connect_args)


def create_db_and_tables():
    SQLModel.metadata.create_all(engine)


app = FastAPI()


@app.on_event("startup")
def on_startup():
    create_db_and_tables()


@app.post("/heroes/", response_model=HeroPublic)
def create_hero(hero: HeroCreate):
    with Session(engine) as session:
        db_hero = Hero.model_validate(hero)
        session.add(db_hero)
        session.commit()
        session.refresh(db_hero)
        return db_hero


@app.get("/heroes/", response_model=list[HeroPublic])
def read_heroes():
    with Session(engine) as session:
        heroes = session.exec(select(Hero)).all()
        return heroes


@app.get("/heroes/{hero_id}", response_model=HeroPublic)
def read_hero(hero_id: int):
    with Session(engine) as session:
        hero = session.get(Hero, hero_id)
        if not hero:
            raise HTTPException(status_code=404, detail="Hero not found")
        return hero

🤓 其他版本和变体

Python 3.9+Python 3.8+

from typing import Optional

from fastapi import FastAPI, HTTPException
from sqlmodel import Field, Session, SQLModel, create_engine, select


class HeroBase(SQLModel):
    name: str = Field(index=True)
    secret_name: str
    age: Optional[int] = Field(default=None, index=True)


class Hero(HeroBase, table=True):
    id: Optional[int] = Field(default=None, primary_key=True)


class HeroCreate(HeroBase):
    pass


class HeroPublic(HeroBase):
    id: int


sqlite_file_name = "database.db"
sqlite_url = f"sqlite:///{sqlite_file_name}"

connect_args = {"check_same_thread": False}
engine = create_engine(sqlite_url, echo=True, connect_args=connect_args)


def create_db_and_tables():
    SQLModel.metadata.create_all(engine)


app = FastAPI()


@app.on_event("startup")
def on_startup():
    create_db_and_tables()


@app.post("/heroes/", response_model=HeroPublic)
def create_hero(hero: HeroCreate):
    with Session(engine) as session:
        db_hero = Hero.model_validate(hero)
        session.add(db_hero)
        session.commit()
        session.refresh(db_hero)
        return db_hero


@app.get("/heroes/", response_model=list[HeroPublic])
def read_heroes():
    with Session(engine) as session:
        heroes = session.exec(select(Hero)).all()
        return heroes


@app.get("/heroes/{hero_id}", response_model=HeroPublic)
def read_hero(hero_id: int):
    with Session(engine) as session:
        hero = session.get(Hero, hero_id)
        if not hero:
            raise HTTPException(status_code=404, detail="Hero not found")
        return hero

from typing import List, Optional

from fastapi import FastAPI, HTTPException
from sqlmodel import Field, Session, SQLModel, create_engine, select


class HeroBase(SQLModel):
    name: str = Field(index=True)
    secret_name: str
    age: Optional[int] = Field(default=None, index=True)


class Hero(HeroBase, table=True):
    id: Optional[int] = Field(default=None, primary_key=True)


class HeroCreate(HeroBase):
    pass


class HeroPublic(HeroBase):
    id: int


sqlite_file_name = "database.db"
sqlite_url = f"sqlite:///{sqlite_file_name}"

connect_args = {"check_same_thread": False}
engine = create_engine(sqlite_url, echo=True, connect_args=connect_args)


def create_db_and_tables():
    SQLModel.metadata.create_all(engine)


app = FastAPI()


@app.on_event("startup")
def on_startup():
    create_db_and_tables()


@app.post("/heroes/", response_model=HeroPublic)
def create_hero(hero: HeroCreate):
    with Session(engine) as session:
        db_hero = Hero.model_validate(hero)
        session.add(db_hero)
        session.commit()
        session.refresh(db_hero)
        return db_hero


@app.get("/heroes/", response_model=List[HeroPublic])
def read_heroes():
    with Session(engine) as session:
        heroes = session.exec(select(Hero)).all()
        return heroes


@app.get("/heroes/{hero_id}", response_model=HeroPublic)
def read_hero(hero_id: int):
    with Session(engine) as session:
        hero = session.get(Hero, hero_id)
        if not hero:
            raise HTTPException(status_code=404, detail="Hero not found")
        return hero

返回英雄

然后，如果英雄存在，我们就返回它。

并且因为我们使用 HeroPublic 的 response_model，它将被验证、记录等。

Python 3.10+

from fastapi import FastAPI, HTTPException
from sqlmodel import Field, Session, SQLModel, create_engine, select

# Code here omitted 👈

@app.get("/heroes/{hero_id}", response_model=HeroPublic)
def read_hero(hero_id: int):
    with Session(engine) as session:
        hero = session.get(Hero, hero_id)
        if not hero:
            raise HTTPException(status_code=404, detail="Hero not found")
        return hero

👀 完整文件预览

Python 3.10+

from fastapi import FastAPI, HTTPException
from sqlmodel import Field, Session, SQLModel, create_engine, select


class HeroBase(SQLModel):
    name: str = Field(index=True)
    secret_name: str
    age: int | None = Field(default=None, index=True)


class Hero(HeroBase, table=True):
    id: int | None = Field(default=None, primary_key=True)


class HeroCreate(HeroBase):
    pass


class HeroPublic(HeroBase):
    id: int


sqlite_file_name = "database.db"
sqlite_url = f"sqlite:///{sqlite_file_name}"

connect_args = {"check_same_thread": False}
engine = create_engine(sqlite_url, echo=True, connect_args=connect_args)


def create_db_and_tables():
    SQLModel.metadata.create_all(engine)


app = FastAPI()


@app.on_event("startup")
def on_startup():
    create_db_and_tables()


@app.post("/heroes/", response_model=HeroPublic)
def create_hero(hero: HeroCreate):
    with Session(engine) as session:
        db_hero = Hero.model_validate(hero)
        session.add(db_hero)
        session.commit()
        session.refresh(db_hero)
        return db_hero


@app.get("/heroes/", response_model=list[HeroPublic])
def read_heroes():
    with Session(engine) as session:
        heroes = session.exec(select(Hero)).all()
        return heroes


@app.get("/heroes/{hero_id}", response_model=HeroPublic)
def read_hero(hero_id: int):
    with Session(engine) as session:
        hero = session.get(Hero, hero_id)
        if not hero:
            raise HTTPException(status_code=404, detail="Hero not found")
        return hero

🤓 其他版本和变体

Python 3.9+Python 3.8+

from typing import Optional

from fastapi import FastAPI, HTTPException
from sqlmodel import Field, Session, SQLModel, create_engine, select


class HeroBase(SQLModel):
    name: str = Field(index=True)
    secret_name: str
    age: Optional[int] = Field(default=None, index=True)


class Hero(HeroBase, table=True):
    id: Optional[int] = Field(default=None, primary_key=True)


class HeroCreate(HeroBase):
    pass


class HeroPublic(HeroBase):
    id: int


sqlite_file_name = "database.db"
sqlite_url = f"sqlite:///{sqlite_file_name}"

connect_args = {"check_same_thread": False}
engine = create_engine(sqlite_url, echo=True, connect_args=connect_args)


def create_db_and_tables():
    SQLModel.metadata.create_all(engine)


app = FastAPI()


@app.on_event("startup")
def on_startup():
    create_db_and_tables()


@app.post("/heroes/", response_model=HeroPublic)
def create_hero(hero: HeroCreate):
    with Session(engine) as session:
        db_hero = Hero.model_validate(hero)
        session.add(db_hero)
        session.commit()
        session.refresh(db_hero)
        return db_hero


@app.get("/heroes/", response_model=list[HeroPublic])
def read_heroes():
    with Session(engine) as session:
        heroes = session.exec(select(Hero)).all()
        return heroes


@app.get("/heroes/{hero_id}", response_model=HeroPublic)
def read_hero(hero_id: int):
    with Session(engine) as session:
        hero = session.get(Hero, hero_id)
        if not hero:
            raise HTTPException(status_code=404, detail="Hero not found")
        return hero

from typing import List, Optional

from fastapi import FastAPI, HTTPException
from sqlmodel import Field, Session, SQLModel, create_engine, select


class HeroBase(SQLModel):
    name: str = Field(index=True)
    secret_name: str
    age: Optional[int] = Field(default=None, index=True)


class Hero(HeroBase, table=True):
    id: Optional[int] = Field(default=None, primary_key=True)


class HeroCreate(HeroBase):
    pass


class HeroPublic(HeroBase):
    id: int


sqlite_file_name = "database.db"
sqlite_url = f"sqlite:///{sqlite_file_name}"

connect_args = {"check_same_thread": False}
engine = create_engine(sqlite_url, echo=True, connect_args=connect_args)


def create_db_and_tables():
    SQLModel.metadata.create_all(engine)


app = FastAPI()


@app.on_event("startup")
def on_startup():
    create_db_and_tables()


@app.post("/heroes/", response_model=HeroPublic)
def create_hero(hero: HeroCreate):
    with Session(engine) as session:
        db_hero = Hero.model_validate(hero)
        session.add(db_hero)
        session.commit()
        session.refresh(db_hero)
        return db_hero


@app.get("/heroes/", response_model=List[HeroPublic])
def read_heroes():
    with Session(engine) as session:
        heroes = session.exec(select(Hero)).all()
        return heroes


@app.get("/heroes/{hero_id}", response_model=HeroPublic)
def read_hero(hero_id: int):
    with Session(engine) as session:
        hero = session.get(Hero, hero_id)
        if not hero:
            raise HTTPException(status_code=404, detail="Hero not found")
        return hero

检查文档 UI

然后我们可以进入文档 UI，查看新的路径操作。

回顾

您可以结合 FastAPI 的功能，例如自动路径参数验证，通过 ID 获取模型。