**FastAPI** 支持同时声明**请求体**、**路径参数**和**查询参数**。

**FastAPI** 能够正确识别这三种参数，并从正确的位置获取数据。

{* ../../docs_src/body/tutorial004_py310.py hl[16] *}

函数参数按如下规则进行识别：

- **路径**中声明了相同参数的参数，是路径参数
- 类型是（`int`、`float`、`str`、`bool` 等）**单类型**的参数，是**查询**参数
- 类型是 **Pydantic 模型**的参数，是**请求体**

/// note | 笔记

因为默认值是 `None`， FastAPI 会把 `q` 当作可选参数。

FastAPI 不使用 `Optional[str]` 中的 `Optional`， 但 `Optional` 可以让编辑器提供更好的支持，并检测错误。

	}

	switch funcName {
	case aggFnCount:
		// For all non-null values, the count is incremented.
		e.aggregate.runningCount++

	case aggFnAvg, aggFnSum:
		e.aggregate.runningCount++
		// Convert to float.
		f, ok := argVal.ToFloat()
		if !ok {
			return fmt.Errorf("Could not convert value %v (%s) to a number", argVal.value, argVal.GetTypeString())
		}
		argVal.setFloat(f)

```Python hl_lines="4  9 10 11 12  25 26 27"
from typing import Union

from fastapi import FastAPI
from pydantic import BaseModel

app = FastAPI()


class Item(BaseModel):
    name: str
    price: float
    is_offer: Union[bool, None] = None


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


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

        if (read(this.tmp, 0, 8) < 0) {
            throw new SmbEndOfFileException();
        }
        return Encdec.dec_uint64be(this.tmp, 0);
    }

    @Override
    public final float readFloat() throws SmbException {
        if (read(this.tmp, 0, 4) < 0) {
            throw new SmbEndOfFileException();
        }
        return Encdec.dec_floatbe(this.tmp, 0);
    }

    @Override

     */
    public String getTrackTotalHits() {
        return null;
    }

    /**
     * Returns the min score.
     *
     * @return The min score.
     */
    public Float getMinScore() {
        return null;
    }

    /**
     * Returns true if the request has a condition query, otherwise false.
     *
     * @return True if the request has a condition query, otherwise false.

{* ../../docs_src/response_model/tutorial004_py310.py hl[9,11:12] *}

* `description: Union[str, None] = None` (o `str | None = None` en Python 3.10) tiene un valor por defecto de `None`.
* `tax: float = 10.5` tiene un valor por defecto de `10.5`.
* `tags: List[str] = []` tiene un valor por defecto de una list vacía: `[]`.

pero podrías querer omitirlos del resultado si no fueron en realidad almacenados.

                            "name": "item_id",
                            "in": "path",
                        }
                    ],
                }
            },
            "/path/float/{item_id}": {
                "get": {
                    "responses": {
                        "200": {
                            "description": "Successful Response",

```Python hl_lines="4  9-12  25-27"
from typing import Union

from fastapi import FastAPI
from pydantic import BaseModel

app = FastAPI()


class Item(BaseModel):
    name: str
    price: float
    is_offer: Union[bool, None] = None


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


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

{* ../../docs_src/response_model/tutorial004_py310.py hl[9,11:12] *}

* `description: Union[str, None] = None` (oder `str | None = None` in Python 3.10) hat einen Defaultwert `None`.
* `tax: float = 10.5` hat einen Defaultwert `10.5`.
* `tags: List[str] = []` hat eine leere Liste als Defaultwert: `[]`.

Aber Sie möchten diese vielleicht vom Resultat ausschließen, wenn Sie gar nicht gesetzt wurden.

        String parentUrl = "https://api.example.com";
        Integer depth = 3;
        Long lastModified = System.currentTimeMillis() - 10000;
        Long createTime = System.currentTimeMillis();
        float weight = 1.5f;

        queue.setId(id);
        queue.setSessionId(sessionId);
        queue.setMethod(method);
        queue.setUrl(url);
        queue.setMetaData(metaData);