In diesem Beispiel wird das Pydantic-Modell in ein `dict`, und das `datetime`-Objekt in ein `str` konvertiert.

Das Resultat dieses Aufrufs ist etwas, das mit Pythons Standard-<a href="https://docs.python.org/3/library/json.html#json.dumps" class="external-link" target="_blank">`json.dumps()`</a> kodiert werden kann.

from fastapi import FastAPI
from pydantic import BaseModel

app = FastAPI()


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


class User(BaseModel):
    username: str
    full_name: Union[str, None] = None


@app.put("/items/{item_id}")
async def update_item(item_id: int, item: Item, user: User):

from fastapi import FastAPI
from pydantic import BaseModel


class Item(BaseModel):
    name: str
    description: str | None = None


app = FastAPI()


@app.post("/items/")
def create_item(item: Item):
    return item


@app.get("/items/")
def read_items() -> list[Item]:
    return [
        Item(
            name="Portal Gun",
            description="Device to travel through the multi-rick-verse",

from typing import Union

from fastapi import Body, FastAPI
from pydantic import BaseModel

app = FastAPI()


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


@app.put("/items/{item_id}")
async def update_item(item_id: int, item: Item = Body(embed=True)):
    results = {"item_id": item_id, "item": item}

本例中，查询参数 `q` 是可选的，默认值为 `None`。

/// check | 检查

注意，**FastAPI** 可以识别出 `item_id` 是路径参数，`q` 不是路径参数，而是查询参数。

///

/// note | 笔记

因为默认值为 `= None`，FastAPI 把 `q` 识别为可选参数。

FastAPI 不使用 `Optional[str]` 中的 `Optional`（只使用 `str`），但 `Optional[str]` 可以帮助编辑器发现代码中的错误。

///

## 查询参数类型转换

参数还可以声明为 `bool` 类型，FastAPI 会自动转换参数类型：


{* ../../docs_src/query_params/tutorial003_py310.py hl[7] *}

本例中，访问：

```

In this example, it would convert the Pydantic model to a `dict`, and the `datetime` to a `str`.

The result of calling it is something that can be encoded with the Python standard <a href="https://docs.python.org/3/library/json.html#json.dumps" class="external-link" target="_blank">`json.dumps()`</a>.

     * Encodes a wide string pointer in NDR format.
     *
     * @param buf the NDR buffer
     * @param str the string to encode (can be null)
     * @throws NdrException if encoding fails
     */
    private void encodeWideStringPointer(NdrBuffer buf, String str) throws NdrException {
        if (str == null || str.isEmpty()) {
            buf.enc_ndr_long(0); // NULL pointer
        } else {

from typing import Annotated

from fastapi import Body, FastAPI
from pydantic import BaseModel

app = FastAPI()


class Item(BaseModel):
    name: str
    description: str | None = None
    price: float
    tax: float | None = None


@app.put("/items/{item_id}")
async def update_item(
    *,
    item_id: int,
    item: Annotated[
        Item,
        Body(
            examples=[
                {

    "management.md",
]


@lru_cache
def get_missing_translation_content(docs_dir: str) -> str:
    docs_dir_path = Path(docs_dir)
    missing_translation_path = docs_dir_path.parent.parent / "missing-translation.md"
    return missing_translation_path.read_text(encoding="utf-8")


@lru_cache
def get_mkdocs_material_langs() -> list[str]:
    material_path = Path(material.__file__).parent

from fastapi import FastAPI
from pydantic import BaseModel


class Item(BaseModel):
    name: str
    description: str | None = None


app = FastAPI(separate_input_output_schemas=False)


@app.post("/items/")
def create_item(item: Item):
    return item


@app.get("/items/")
def read_items() -> list[Item]:
    return [
        Item(
            name="Portal Gun",