```Python hl_lines="2  7-10 23-25"
from fastapi import FastAPI
from pydantic import BaseModel

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):

{
    "name": "Bar",
    "description": "The bartenders",
    "price": 62,
    "tax": 20.2
}
```

它們會被包含在回應中。

#### 與預設值相同的資料 { #data-with-the-same-values-as-the-defaults }

如果資料的值與預設值相同，例如 ID 為 `baz` 的項目：

```Python hl_lines="3  5-6"
{
    "name": "Baz",
    "description": None,
    "price": 50.2,
    "tax": 10.5,
    "tags": []
}
```

        // Both instances should be of the same class
        assertEquals(exception1.getClass(), exception2.getClass());
    }

    @Test
    public void test_stackTracePopulated() {
        // Test that stack trace is properly populated
        InvalidAccessTokenException exception = new InvalidAccessTokenException("JWT", "Invalid signature");

        StackTraceElement[] stackTrace = exception.getStackTrace();

Connections
===========

Although you provide only the URL, OkHttp plans its connection to your webserver using three types: URL, Address, and Route.

### [URLs](https://square.github.io/okhttp/5.x/okhttp/okhttp3/-http-url/)

URLs (like `https://github.com/square/okhttp`) are fundamental to HTTP and the Internet. In addition to being a universal, decentralized naming scheme for everything on the web, they also specify how to access web resources.

            Subject s = lc.getSubject();
            if (log.isDebugEnabled()) {
                log.debug("Got subject: " + s.getPrincipals());
            }
            if (log.isTraceEnabled()) {
                log.trace("Got subject " + s);
            }

            this.cachedSubject = s;
            return this.cachedSubject;
        } catch (LoginException e) {
            log.error("Failed to create login context", e);

This is not particular to FastAPI, it's just Python, but it's a nice trick to know. 😎

                        this.sizeExpiration = currentTime + cacheTimeout;
                        log.trace("Retrieved size info in additional query: {}", this.size);
                    }
                } catch (CIFSException e) {
                    // Size query failed, but we have basic info - continue
                    log.trace("Size query failed, continuing with basic info", e);
                }
            }

// - SOSAPI Protocol Version
// - Model Name of the vendor plus version for statistical analysis.
// - List of Smart Object Storage protocol capabilities supported by the server.
// Currently, there are three capabilities supported:
//   - Capacity Reporting
//   - Backup data locality for upload sessions (Veeam Smart Entity)

      cp >>>= 2;
      dest[2] = upperHexDigits[cp & 0xF];
      cp >>>= 4;
      dest[1] = upperHexDigits[0xC | cp];
      return dest;
    } else if (cp <= 0xffff) {
      // Three byte UTF-8 characters [cp >= 0x800 && cp <= 0xffff]
      // Start with "%E-%--%--" and fill in the blanks
      char[] dest = new char[9];
      dest[0] = '%';
      dest[1] = 'E';
      dest[3] = '%';

現在你可以匯入並使用用戶端程式碼。大致看起來會像這樣，你會發現方法有自動完成：

<img src="/img/tutorial/generate-clients/image02.png">

你也會對要送出的有效載荷獲得自動完成：

<img src="/img/tutorial/generate-clients/image03.png">

/// tip

注意 `name` 與 `price` 的自動完成，這是由 FastAPI 應用中的 `Item` 模型所定義。

///

你在送出的資料上也會看到行內錯誤：

<img src="/img/tutorial/generate-clients/image04.png">

回應物件同樣有自動完成：

<img src="/img/tutorial/generate-clients/image05.png">