from fastapi import FastAPI
from fastapi.testclient import TestClient
from pydantic import BaseModel

app = FastAPI()


class UserCreate(BaseModel):
    email: str
    password: str


class UserDB(BaseModel):
    email: str
    hashed_password: str


class User(BaseModel):
    email: str


class PetDB(BaseModel):
    name: str
    owner: UserDB


class PetOut(BaseModel):
    name: str

import pytest
from fastapi import FastAPI
from fastapi.testclient import TestClient


@pytest.fixture(name="app", scope="module")
def get_app():
    with pytest.warns(DeprecationWarning):
        from docs_src.events.tutorial001_py39 import app
    yield app


def test_events(app: FastAPI):
    with TestClient(app) as client:
        response = client.get("/items/foo")
        assert response.status_code == 200, response.text

     *            The {@link Reader} to read strings from. Must not be {@literal null}.
     */
    public LineIterator(final Reader reader) {
        assertArgumentNotNull("reader", reader);
        this.reader = new BufferedReader(reader);
    }

    /**
     * Constructs an instance.
     *
     * @param reader
     *            The {@link BufferedReader} to read strings from. Must not be {@literal null}.
     */

        return total;
      }
    },
    NEW {
      @Override
      long copy(Readable from, Appendable to) throws IOException {
        return CharStreams.copy(from, to);
      }
    };

    abstract long copy(Readable from, Appendable to) throws IOException;
  }

  enum TargetSupplier {
    STRING_WRITER {
      @Override
      Appendable get(int sz) {
        return new StringWriter(sz);
      }
    },

from typing import Union

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
    tags: list = []


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

from typing import Annotated, Union

from fastapi import FastAPI, Header
from pydantic import BaseModel

app = FastAPI()


class CommonHeaders(BaseModel):
    model_config = {"extra": "forbid"}

    host: str
    save_data: bool
    if_modified_since: Union[str, None] = None
    traceparent: Union[str, None] = None
    x_tag: list[str] = []


@app.get("/items/")

from fastapi import FastAPI
from pydantic import BaseModel as BaseModelV2
from pydantic.v1 import BaseModel


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


class ItemV2(BaseModelV2):
    name: str
    description: str | None = None
    size: float


app = FastAPI()


@app.post("/items/", response_model=ItemV2)
async def create_item(item: Item):

There are several custom response classes you can use to create an instance and return them directly from your *path operations*.

Read more about it in the [FastAPI docs for Custom Response - HTML, Stream, File, others](https://fastapi.tiangolo.com/advanced/custom-response/).

You can import them directly from `fastapi.responses`:

```python
from fastapi.responses import (
    FileResponse,
    HTMLResponse,
    JSONResponse,

from typing import Annotated

import pytest
from fastapi import FastAPI, Path
from fastapi.testclient import TestClient

app = FastAPI()


@app.get("/required-str/{p}")
async def read_required_str(p: Annotated[str, Path()]):
    return {"p": p}


@app.get("/required-alias/{p_alias}")
async def read_required_alias(p: Annotated[str, Path(alias="p_alias")]):
    return {"p": p}

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=[
                {