from typing import List, Union

from fastapi import FastAPI
from fastapi.encoders import jsonable_encoder
from pydantic import BaseModel

app = FastAPI()


class Item(BaseModel):
    name: Union[str, None] = None
    description: Union[str, None] = None
    price: Union[float, None] = None
    tax: float = 10.5
    tags: List[str] = []


items = {
    "foo": {"name": "Foo", "price": 50.2},

By default, **FastAPI** would automatically convert that return value to JSON using the `jsonable_encoder` explained in [JSON Compatible Encoder](../tutorial/encoder.md){.internal-link target=_blank}.

Then, behind the scenes, it would put that JSON-compatible data (e.g. a `dict`) inside of a `JSONResponse` that would be used to send the response to the client.

## Convert any Data to JSON-compatible

To convert any data to JSON-compatible, read the docs for [Tutorial - JSON Compatible Encoder](../tutorial/encoder.md){.internal-link target=_blank}.

## OpenAPI Metadata - Docs

/// info | "信息"

注意 `TestClient` 接收可以被转化为JSON的数据，而不是Pydantic模型。

如果你在测试中有一个Pydantic模型，并且你想在测试时发送它的数据给应用，你可以使用在[JSON Compatible Encoder](encoder.md){.internal-link target=_blank}介绍的`jsonable_encoder` 。

///

## 运行起来

之后，你只需要安装 `pytest`:

<div class="termy">

```console
$ pip install pytest

---> 100%
```

	var s string
	if err = d.DecodeElement(&s, &start); err != nil {
		return err
	}
	*p = Prefix{string: s, set: true}
	return nil
}

// MarshalXML - decodes XML data.
func (p Prefix) MarshalXML(e *xml.Encoder, startElement xml.StartElement) error {
	if !p.set {
		return nil
	}
	return e.EncodeElement(p.string, startElement)
}

// String returns the prefix string
func (p Prefix) String() string {
	return p.string

	}

	*tDate = TransitionDate{trnDate}
	return nil
}

// MarshalXML encodes expiration date if it is non-zero and encodes
// empty string otherwise
func (tDate TransitionDate) MarshalXML(e *xml.Encoder, startElement xml.StartElement) error {
	if tDate.Time.IsZero() {
		return nil
	}
	return e.EncodeElement(tDate.Format(time.RFC3339), startElement)
}

// TransitionDays is a type alias to unmarshal Days in Transition

Par défaut, **FastAPI** convertirait automatiquement cette valeur de retour en JSON en utilisant le `jsonable_encoder` expliqué dans [JSON Compatible Encoder](../tutorial/encoder.md){.internal-link target=_blank}.

Ensuite, en arrière-plan, il mettra ces données JSON-compatible (par exemple un `dict`) à l'intérieur d'un `JSONResponse` qui sera utilisé pour envoyer la réponse au client.

from datetime import datetime
from typing import Union

from fastapi import FastAPI
from fastapi.encoders import jsonable_encoder
from fastapi.responses import JSONResponse
from pydantic import BaseModel


class Item(BaseModel):
    title: str
    timestamp: datetime
    description: Union[str, None] = None


app = FastAPI()


@app.put("/items/{id}")
def update_item(id: str, item: Item):

from fastapi import FastAPI, Request, status
from fastapi.encoders import jsonable_encoder
from fastapi.exceptions import RequestValidationError
from fastapi.responses import JSONResponse
from pydantic import BaseModel

app = FastAPI()


@app.exception_handler(RequestValidationError)
async def validation_exception_handler(request: Request, exc: RequestValidationError):
    return JSONResponse(
        status_code=status.HTTP_422_UNPROCESSABLE_ENTITY,

	set                     bool
}

// MarshalXML if non-current days not set to non zero value
func (n NoncurrentVersionExpiration) MarshalXML(e *xml.Encoder, start xml.StartElement) error {
	if n.IsNull() {
		return nil
	}
	type noncurrentVersionExpirationWrapper NoncurrentVersionExpiration
	return e.EncodeElement(noncurrentVersionExpirationWrapper(n), start)
}