from fastapi import FastAPI, Request
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=422,

from datetime import datetime
from typing import Union

from pydantic import BaseModel


class User(BaseModel):
    id: int
    name: str = "John Doe"
    signup_ts: Union[datetime, None] = None
    friends: list[int] = []


external_data = {
    "id": "123",
    "signup_ts": "2017-06-01 12:22",
    "friends": [1, "2", b"3"],
}
user = User(**external_data)
print(user)

///

## Exclude from OpenAPI { #exclude-from-openapi }

To exclude a *path operation* from the generated OpenAPI schema (and thus, from the automatic documentation systems), use the parameter `include_in_schema` and set it to `False`:

{* ../../docs_src/path_operation_advanced_configuration/tutorial003_py39.py hl[6] *}

## Advanced description from docstring { #advanced-description-from-docstring }

import functools

from fastapi import FastAPI
from fastapi.testclient import TestClient

from .forward_reference_type import forwardref_method


def passthrough(f):
    @functools.wraps(f)
    def method(*args, **kwargs):
        return f(*args, **kwargs)

    return method


def test_wrapped_method_type_inference():
    """
    Regression test ensuring that when a method imported from another module

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


class Item(BaseModel):
    id: str
    value: str


class Message(BaseModel):
    message: str


app = FastAPI()


@app.get("/items/{item_id}", response_model=Item, responses={404: {"model": Message}})
async def read_item(item_id: str):
    if item_id == "foo":

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(
        examples=[
            {
                "name": "Foo",

from typing import Annotated

import pytest
from fastapi import Depends, FastAPI, Path
from fastapi.param_functions import Query
from fastapi.testclient import TestClient

app = FastAPI()


def test_no_annotated_defaults():
    with pytest.raises(
        AssertionError, match="Path parameters cannot have a default value"
    ):

        @app.get("/items/{item_id}/")
        async def get_item(item_id: Annotated[int, Path(default=1)]):

You can also use it directly to create an instance of it and return it from your *path operations*.

You can import it directly from `fastapi`:

```python
from fastapi import Response
```

from typing import Union

from fastapi import FastAPI
from pydantic import BaseModel, Field

app = FastAPI()


class Item(BaseModel):
    name: str = Field(examples=["Foo"])
    description: Union[str, None] = Field(default=None, examples=["A very nice Item"])
    price: float = Field(examples=[35.4])
    tax: Union[float, None] = Field(default=None, examples=[3.2])


@app.put("/items/{item_id}")

     *
     * @return The model identifiers from the lineage of models, never {@code null}.
     */
    List<String> getModelIds();

    /**
     * Gets the assembled model.
     *
     * @return The assembled model, never {@code null}.
     */
    Model getEffectiveModel();

    /**
     * Gets the raw model as it was read from the input model source. Apart from basic validation, the raw model has not