from typing import Annotated

from fastapi import FastAPI, Query

app = FastAPI()


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

from fastapi import FastAPI, Query

app = FastAPI()


@app.get("/items/")
async def read_items(
    q: str | None = Query(default=None, title="Query string", min_length=3),
):
    results = {"items": [{"item_id": "Foo"}, {"item_id": "Bar"}]}
    if q:
        results.update({"q": q})

    "user": {
        "username": "dave",
        "full_name": "Dave Grohl"
    }
}
```

/// note | Not

`item` daha öncekiyle aynı şekilde tanımlanmış olsa bile, artık body içinde `item` anahtarı altında gelmesi beklenir.

///

**FastAPI**, request'ten otomatik dönüşümü yapar; böylece `item` parametresi kendi içeriğini alır, `user` için de aynı şekilde olur.

from typing import Annotated

from fastapi import FastAPI, Query

app = FastAPI()


@app.get("/items/")
async def read_items(q: Annotated[str | None, Query(max_length=50)] = None):
    results = {"items": [{"item_id": "Foo"}, {"item_id": "Bar"}]}
    if q:
        results.update({"q": q})

constraints.URL.message = {item} is not a valid URL.
constraints.Required.message = {item} is required.
constraints.TypeInteger.message = {item} must be a number.
constraints.TypeLong.message = {item} must be a number.
constraints.TypeFloat.message = {item} must be a number.
constraints.TypeDouble.message = {item} must be a number.
constraints.TypeAny.message = {item} cannot be converted to {propertyType}.
constraints.UriType.message = {item} has an unrecognized URI.

constraints.URL.message = {item} is not a valid URL.
constraints.Required.message = {item} is required.
constraints.TypeInteger.message = {item} must be a number.
constraints.TypeLong.message = {item} must be a number.
constraints.TypeFloat.message = {item} must be a number.
constraints.TypeDouble.message = {item} must be a number.
constraints.TypeAny.message = {item} cannot be converted to {propertyType}.
constraints.UriType.message = {item} has an unrecognized URI.

Und wenn Sie den Scope `me`, aber nicht den Scope `items` auswählen, können Sie auf `/users/me/` zugreifen, aber nicht auf `/users/me/items/`.

    String simple = "a,b,c,d";
    Iterable<String> items = COMMA_SPLITTER.limit(1).split(simple);
    assertThat(items).containsExactly("a,b,c,d").inOrder();
  }

  public void testLimitSeparator() {
    String simple = "a,b,c,d";
    Iterable<String> items = COMMA_SPLITTER.limit(2).split(simple);
    assertThat(items).containsExactly("a", "b,c,d").inOrder();
  }

O valor do parâmetro de path `item_id` será passado para a sua função como o argumento `item_id`.

Então, se você executar este exemplo e acessar [http://127.0.0.1:8000/items/foo](http://127.0.0.1:8000/items/foo), você verá uma resposta:

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

## Parâmetros de path com tipos { #path-parameters-with-types }

运行示例并访问 [http://127.0.0.1:8000/items/3](http://127.0.0.1:8000/items/3)，返回的响应如下：

```JSON
{"item_id":3}
```

/// check | 检查

注意，函数接收并返回的值是 `3`（ `int`），不是 `"3"`（`str`）。

**FastAPI** 通过类型声明自动进行请求的<dfn title="将来自 HTTP 请求中的字符串转换为 Python 数据类型">解析</dfn>。

///

## 数据校验 { #data-validation }

通过浏览器访问 [http://127.0.0.1:8000/items/foo](http://127.0.0.1:8000/items/foo)，接收如下 HTTP 错误信息：

```JSON
{