from fastapi import FastAPI, Response

app = FastAPI()


@app.get("/headers-and-object/")
def get_headers(response: Response):
    response.headers["X-Cat-Dog"] = "alone in the world"

from typing import Union

from fastapi import FastAPI, Header

app = FastAPI()


@app.get("/items/")
async def read_items(
    strange_header: Union[str, None] = Header(default=None, convert_underscores=False),
):

from typing import Optional

from fastapi.openapi.models import OpenIdConnect as OpenIdConnectModel
from fastapi.security.base import SecurityBase
from starlette.exceptions import HTTPException
from starlette.requests import Request
from starlette.status import HTTP_403_FORBIDDEN
from typing_extensions import Annotated, Doc


class OpenIdConnect(SecurityBase):
    """
    OpenID Connect authentication class. An instance of it would be used as a

import os
import shutil

from dirty_equals import IsDict
from fastapi.testclient import TestClient

from docs_src.additional_responses.tutorial002 import app

client = TestClient(app)


def test_path_operation():
    response = client.get("/items/foo")
    assert response.status_code == 200, response.text
    assert response.json() == {"id": "foo", "value": "there goes my hero"}


def test_path_operation_img():

import pytest
from fastapi.testclient import TestClient

from ...utils import needs_py310, needs_pydanticv2


@pytest.fixture(name="client")
def get_client() -> TestClient:
    from docs_src.separate_openapi_schemas.tutorial001_py310 import app

    client = TestClient(app)
    return client


@needs_py310
def test_create_item(client: TestClient) -> None:
    response = client.post("/items/", json={"name": "Foo"})

import pytest
from fastapi.testclient import TestClient

from ...utils import needs_pydanticv2


@pytest.fixture(name="client")
def get_client() -> TestClient:
    from docs_src.separate_openapi_schemas.tutorial002 import app

    client = TestClient(app)
    return client


def test_create_item(client: TestClient) -> None:
    response = client.post("/items/", json={"name": "Foo"})
    assert response.status_code == 200, response.text

import uvicorn
from fastapi import FastAPI

app = FastAPI()


@app.get("/")
def root():
    a = "a"
    b = "b" + a
    return {"hello world": b}


if __name__ == "__main__":

# Sub-dependencies

You can create dependencies that have **sub-dependencies**.

They can be as **deep** as you need them to be.

**FastAPI** will take care of solving them.

## First dependency "dependable"

You could create a first dependency ("dependable") like:

//// tab | Python 3.10+

```Python hl_lines="8-9"
{!> ../../docs_src/dependencies/tutorial005_an_py310.py!}
```

////

//// tab | Python 3.9+

from typing import List

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

app = FastAPI()


class UserBase(BaseModel):
    email: str


class UserCreate(UserBase):
    password: str


class UserDB(UserBase):
    hashed_password: str


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


class PetOut(BaseModel):
    name: str

from fastapi import FastAPI, Query

app = FastAPI()


@app.get("/items/")
async def read_items(q: str = Query(default=..., min_length=3)):
    results = {"items": [{"item_id": "Foo"}, {"item_id": "Bar"}]}
    if q:
        results.update({"q": q})