```

The value of the path parameter `item_id` will be passed to your function as the argument `item_id`.

So, if you run this example and go to <a href="http://127.0.0.1:8000/items/foo" class="external-link" target="_blank">http://127.0.0.1:8000/items/foo</a>, you will see a response of:

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

## Path parameters with types

运行示例并访问 <a href="http://127.0.0.1:8000/items/3" class="external-link" target="_blank">http://127.0.0.1:8000/items/3</a>，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<abbr title="将来自 HTTP 请求中的字符串转换为 Python 数据类型">**解析**请求中的数据</abbr>。

## 数据校验

其余的请求则会被 **FastAPI** 处理。

如果您使用 Uvicorn 运行应用实例并且访问 <a href="http://localhost:8000/v1/" class="external-link" target="_blank">http://localhost:8000/v1/</a>，您将会看到由 Flask 返回的响应：

```txt
Hello, World from Flask!
```

并且如果您访问 <a href="http://localhost:8000/v2" class="external-link" target="_blank">http://localhost:8000/v2</a>，您将会看到由 FastAPI 返回的响应：

```JSON
{
    "message": "Hello World"
}

```hl_lines="4"
INFO:     Uvicorn running on http://127.0.0.1:8000 (Press CTRL+C to quit)
```

👈 ⏸ 🎦 📛 🌐❔ 👆 📱 ➖ 🍦, 👆 🇧🇿 🎰.

### ✅ ⚫️

📂 👆 🖥 <a href="http://127.0.0.1:8000" class="external-link" target="_blank">http://127.0.0.1:8000</a>.

👆 🔜 👀 🎻 📨:

```JSON
{"message": "Hello World"}
```

### 🎓 🛠️ 🩺

```Python
    uvicorn.run(app, host="0.0.0.0", port=8000)
```

이 실행됩니다.

---

해당 모듈(파일)을 가져오면 이런 일이 발생하지 않습니다

그래서 다음과 같은 다른 파일 `importer.py`가 있는 경우:

```Python
from myapp import app

# Some more code
```

이 경우 `myapp.py` 내부의 자동 변수에는 값이 `"__main__"`인 변수 `__name__`이 없습니다.

따라서 다음 행

```Python
    uvicorn.run(app, host="0.0.0.0", port=8000)
```

은 실행되지 않습니다.

!!! info "정보"

from fastapi import FastAPI

app = FastAPI()


@app.get("/")
def root():
    a = "a"
    b = "b" + a
    return {"hello world": b}


if __name__ == "__main__":

from typing_extensions import Annotated

app = FastAPI()


@app.get("/items/{item_id}")
async def read_items(
    *,
    item_id: Annotated[int, Path(title="The ID of the item to get", ge=0, le=1000)],
    q: str,
    size: Annotated[float, Query(gt=0, lt=10.5)],
):
    results = {"item_id": item_id}
    if q:
        results.update({"q": q})

    price: float
    tax: Union[float, None] = None


@app.put("/items/{item_id}")
async def update_item(
    *,
    item_id: int = Path(title="The ID of the item to get", ge=0, le=1000),
    q: Union[str, None] = None,
    item: Union[Item, None] = None,
):
    results = {"item_id": item_id}
    if q:
        results.update({"q": q})
    if item:
        results.update({"item": item})

🔜 👆 💪 ❎ `.openapi()` 👩‍🔬 ⏮️ 👆 🆕 🔢.

```Python hl_lines="28"
{!../../../docs_src/extending_openapi/tutorial001.py!}
```

### ✅ ⚫️

🕐 👆 🚶 <a href="http://127.0.0.1:8000/redoc" class="external-link" target="_blank">http://127.0.0.1:8000/redoc</a> 👆 🔜 👀 👈 👆 ⚙️ 👆 🛃 🔱 (👉 🖼, **FastAPI**'Ⓜ 🔱):

def run(playwright: Playwright) -> None:
    browser = playwright.chromium.launch(headless=False)
    context = browser.new_context(viewport={"width": 960, "height": 1080})
    page = context.new_page()
    page.goto("http://localhost:8000/docs")
    page.get_by_text("GET/items/Read Items").click()
    page.get_by_role("tab", name="Schema").click()
    page.get_by_label("Schema").get_by_role("button", name="Expand all").click()
    page.screenshot(