@app.get("/")
def read_root():
    return {"Hello": "World"}


@app.get("/items/{item_id}")
def read_item(item_id: int, q: str | None = None):
    return {"item_id": item_id, "q": q}


@app.put("/items/{item_id}")
def update_item(item_id: int, item: Item):
    return {"item_name": item.name, "item_id": item_id}
```

Le serveur `fastapi dev` devrait se recharger automatiquement.

    except OwnerError as e:
        raise HTTPException(status_code=400, detail=f"Owner error: {e}")


@app.get("/items/{item_id}")
def get_item(item_id: str, username: Annotated[str, Depends(get_username)]):
    if item_id not in data:
        raise HTTPException(status_code=404, detail="Item not found")
    item = data[item_id]
    if item["owner"] != username:
        raise OwnerError(username)

            "info": {"title": "FastAPI", "version": "0.1.0"},
            "paths": {
                "/items/{item_id}": {
                    "put": {
                        "parameters": [
                            {
                                "in": "path",
                                "name": "item_id",
                                "required": True,
                                "schema": {

路径参数 `item_id` 的值会作为参数 `item_id` 传递给你的函数。

运行示例并访问 [http://127.0.0.1:8000/items/foo](http://127.0.0.1:8000/items/foo)，可获得如下响应：

```JSON
{"item_id":"foo"}
```

## 声明路径参数的类型 { #path-parameters-with-types }

使用 Python 标准类型注解，声明路径操作函数中路径参数的类型：

{* ../../docs_src/path_params/tutorial002_py310.py hl[7] *}

本例把 `item_id` 的类型声明为 `int`。

/// check | 检查

@app.get("/")
def read_root():
    return {"Hello": "World"}


@app.get("/items/{item_id}")
def read_item(item_id: int, q: str | None = None):
    return {"item_id": item_id, "q": q}


@app.put("/items/{item_id}")
def update_item(item_id: int, item: Item):
    return {"item_name": item.name, "item_id": item_id}
```

The `fastapi dev` server should reload automatically.

app = FastAPI()


class Item(BaseModel):
    name: str
    description: str | None = None
    price: float
    tax: float | None = None


@app.put("/items/{item_id}")
async def update_item(
    *,
    item_id: int,
    item: Annotated[
        Item,
        Body(
            openapi_examples={
                "normal": {
                    "summary": "A normal example",

    description: str | None = None


@app.get("/items/{item_id}", response_model=Item)
async def read_main(item_id: str, x_token: str = Header()):
    if x_token != fake_secret_token:
        raise HTTPException(status_code=400, detail="Invalid X-Token header")
    if item_id not in fake_db:
        raise HTTPException(status_code=404, detail="Item not found")
    return fake_db[item_id]


@app.post("/items/")

@app.get("/")
def read_root():
    return {"Hello": "World"}


@app.get("/items/{item_id}")
def read_item(item_id: int, q: str | None = None):
    return {"item_id": item_id, "q": q}


@app.put("/items/{item_id}")
def update_item(item_id: int, item: Item):
    return {"item_name": item.name, "item_id": item_id}
```

`fastapi dev` 伺服器應會自動重新載入。

### 互動式 API 文件升級 { #interactive-api-docs-upgrade }

///

## Declare metadata { #declare-metadata }

You can declare all the same parameters as for `Query`.

For example, to declare a `title` metadata value for the path parameter `item_id` you can type:

{* ../../docs_src/path_params_numeric_validations/tutorial001_an_py310.py hl[10] *}

/// note

from fastapi import FastAPI, Query

app = FastAPI()


@app.get("/items/")
async def read_items(q: str = Query(min_length=3)):
    results = {"items": [{"item_id": "Foo"}, {"item_id": "Bar"}]}
    if q:
        results.update({"q": q})