"paths": {
                "/items/{item_id}": {
                    "put": {
                        "parameters": [
                            {
                                "in": "path",
                                "name": "item_id",
                                "required": True,
                                "schema": {
                                    "title": "Item Id",

            "paths": {
                "/items/{item_id}": {
                    "put": {
                        "parameters": [
                            {
                                "in": "path",
                                "name": "item_id",
                                "required": True,
                                "schema": {
                                    "title": "Item Id",

            "paths": {
                "/items/{item_id}": {
                    "put": {
                        "parameters": [
                            {
                                "in": "path",
                                "name": "item_id",
                                "required": True,
                                "schema": {
                                    "title": "Item Id",

app = FastAPI()


class Item(BaseModel):
    name: str
    price: float
    is_offer: bool | None = None


@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):

用浏览器打开 [http://127.0.0.1:8000/items/5?q=somequery](http://127.0.0.1:8000/items/5?q=somequery)。

你会看到如下 JSON 响应：

```JSON
{"item_id": 5, "q": "somequery"}
```

你已经创建了一个 API，它可以：

* 在路径 `/` 和 `/items/{item_id}` 接收 HTTP 请求。
* 以上两个路径都接受 `GET` 操作（也称为 HTTP 方法）。
* 路径 `/items/{item_id}` 有一个应为 `int` 的路径参数 `item_id`。
* 路径 `/items/{item_id}` 有一个可选的 `str` 类型查询参数 `q`。

Der Wert des Pfad-Parameters `item_id` wird Ihrer Funktion als das Argument `item_id` übergeben.

Wenn Sie dieses Beispiel ausführen und auf [http://127.0.0.1:8000/items/foo](http://127.0.0.1:8000/items/foo) gehen, sehen Sie als <abbr title="Response – Antwort: Daten, die der Server zum anfragenden Client zurücksendet">Response</abbr>:

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

        assertFalse(item1.equals(item3));

        // Item with null output should not equal item with different inputs
        CharMappingItem item4 = new CharMappingItem(4L, inputs3, null);
        assertFalse(item1.equals(item4));

        // Symmetry
        assertTrue(item1.equals(item2));
        assertTrue(item2.equals(item1));
    }

    @Test
    public void test_toString() {

            "info": {"title": "FastAPI", "version": "0.1.0"},
            "paths": {
                "/items/{item_id}": {
                    "get": {
                        "responses": {
                            "200": {
                                "description": "Return the JSON item or an image.",
                                "content": {
                                    "image/png": {},

from fastapi import FastAPI, Query

app = FastAPI()


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