from fastapi import FastAPI

app = FastAPI()


@app.get("/")
async def read_main():

from fastapi import FastAPI

app = FastAPI()


@app.get("/")
async def root():

```


/// note | "技术细节"

你也可以使用`from starlette.responses import Response`或`from starlette.responses import JSONResponse`。

**FastAPI**提供了与`fastapi.responses`相同的`starlette.responses`，只是为了方便开发者。但是，大多数可用的响应都直接来自Starlette。

由于`Response`经常用于设置头部和cookies，因此**FastAPI**还在`fastapi.Response`中提供了它。

///

## 自定义头部

请注意，可以使用'X-'前缀添加自定义专有头部。

from typing import Union

from fastapi import Body, FastAPI
from pydantic import BaseModel

app = FastAPI()


class Item(BaseModel):
    name: str
    description: Union[str, None] = None
    price: float
    tax: Union[float, None] = None


@app.put("/items/{item_id}")
async def update_item(
    *,
    item_id: int,
    item: Item = Body(
        examples=[
            {
                "name": "Foo",

from typing import Union

from fastapi import FastAPI
from pydantic import BaseModel

app = FastAPI()


class Item(BaseModel):
    name: str
    description: Union[str, None] = None
    price: float
    tax: Union[float, None] = None
    tags: set[str] = set()


@app.post("/items/", response_model=Item, tags=["items"])
async def create_item(item: Item):
    return item


@app.get("/items/", tags=["items"])

 & ⚫️ 🔜 ✔️ 👯‍♂️ 📨 🧾, 1️⃣ `404` & 1️⃣ `403`.

///

## 👑 `FastAPI`

🔜, ➡️ 👀 🕹 `app/main.py`.

📥 🌐❔ 👆 🗄 & ⚙️ 🎓 `FastAPI`.

👉 🔜 👑 📁 👆 🈸 👈 👔 🌐 👯‍♂️.

& 🏆 👆 ⚛ 🔜 🔜 🖖 🚮 👍 🎯 🕹, 👑 📁 🔜 🙅.

### 🗄 `FastAPI`

👆 🗄 & ✍ `FastAPI` 🎓 🛎.

from typing import Union

from fastapi import BackgroundTasks, Depends, FastAPI

app = FastAPI()


def write_log(message: str):
    with open("log.txt", mode="a") as log:
        log.write(message)


def get_query(background_tasks: BackgroundTasks, q: Union[str, None] = None):
    if q:
        message = f"found query: {q}\n"
        background_tasks.add_task(write_log, message)
    return q

from fastapi import FastAPI
from pydantic import BaseModel

app = FastAPI()


class Item(BaseModel):
    name: str
    price: float


class ResponseMessage(BaseModel):
    message: str


class User(BaseModel):
    username: str
    email: str


@app.post("/items/", response_model=ResponseMessage, tags=["items"])
async def create_item(item: Item):
    return {"message": "Item received"}

A **FastAPI** saberá que pode usar essa dependência para definir um "esquema de segurança" no esquema da OpenAPI (e na documentação da API automática).

/// info | "Detalhes técnicos"



///

You can import it directly from `fastapi`:

```python
from fastapi import Request
```

/// tip

When you want to define dependencies that should be compatible with both HTTP and WebSockets, you can define a parameter that takes an `HTTPConnection` instead of a `Request` or a `WebSocket`.

///