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docs_src/path_operation_configuration/tutorial006_py310.py

from fastapi import FastAPI

app = FastAPI()


@app.get("/items/", tags=["items"])
async def read_items():
    return [{"name": "Foo", "price": 42}]


@app.get("/users/", tags=["users"])
async def read_users():
    return [{"username": "johndoe"}]


@app.get("/elements/", tags=["items"], deprecated=True)
async def read_elements():

Created: Sun Apr 05 07:19:11 GMT 2026

- Last Modified: Thu Feb 12 13:19:43 GMT 2026

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github.com/tiangolo/fastapi

tests/test_http_connection_injection.py

from starlette.websockets import WebSocket

app = FastAPI()
app.state.value = 42


async def extract_value_from_http_connection(conn: HTTPConnection):
    return conn.app.state.value


@app.get("/http")
async def get_value_by_http(value: int = Depends(extract_value_from_http_connection)):
    return value


@app.websocket("/ws")
async def get_value_by_ws(

Created: Sun Apr 05 07:19:11 GMT 2026

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github.com/tiangolo/fastapi

docs_src/bigger_applications/app_an_py310/routers/items.py

    responses={404: {"description": "Not found"}},
)


fake_items_db = {"plumbus": {"name": "Plumbus"}, "gun": {"name": "Portal Gun"}}


@router.get("/")
async def read_items():
    return fake_items_db


@router.get("/{item_id}")
async def read_item(item_id: str):
    if item_id not in fake_items_db:
        raise HTTPException(status_code=404, detail="Item not found")

Created: Sun Apr 05 07:19:11 GMT 2026

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github.com/tiangolo/fastapi

docs_src/custom_request_and_route/tutorial003_py310.py

            return response

        return custom_route_handler


app = FastAPI()
router = APIRouter(route_class=TimedRoute)


@app.get("/")
async def not_timed():
    return {"message": "Not timed"}


@router.get("/timed")
async def timed():
    return {"message": "It's the time of my life"}

Created: Sun Apr 05 07:19:11 GMT 2026

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github.com/tiangolo/fastapi

tests/test_annotated.py

from inline_snapshot import snapshot

app = FastAPI()


@app.get("/default")
async def default(foo: Annotated[str, Query()] = "foo"):
    return {"foo": foo}


@app.get("/required")
async def required(foo: Annotated[str, Query(min_length=1)]):
    return {"foo": foo}


@app.get("/multiple")
async def multiple(foo: Annotated[str, object(), Query(min_length=1)]):
    return {"foo": foo}

Created: Sun Apr 05 07:19:11 GMT 2026

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github.com/tiangolo/fastapi

tests/test_dependency_overrides.py

app = FastAPI()

router = APIRouter()


async def common_parameters(q: str, skip: int = 0, limit: int = 100):
    return {"q": q, "skip": skip, "limit": limit}


@app.get("/main-depends/")
async def main_depends(commons: dict = Depends(common_parameters)):
    return {"in": "main-depends", "params": commons}


@app.get("/decorator-depends/", dependencies=[Depends(common_parameters)])
async def decorator_depends():

Created: Sun Apr 05 07:19:11 GMT 2026

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github.com/tiangolo/fastapi

docs_src/generate_clients/tutorial002_py310.py

async def create_item(item: Item):
    return {"message": "Item received"}


@app.get("/items/", response_model=list[Item], tags=["items"])
async def get_items():
    return [
        {"name": "Plumbus", "price": 3},
        {"name": "Portal Gun", "price": 9001},
    ]


@app.post("/users/", response_model=ResponseMessage, tags=["users"])
async def create_user(user: User):

Created: Sun Apr 05 07:19:11 GMT 2026

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github.com/tiangolo/fastapi

fastapi/.agents/skills/fastapi/references/streaming.md

# Streaming

## Stream JSON Lines

To stream JSON Lines, declare the return type and use `yield` to return the data.

```python
@app.get("/items/stream")
async def stream_items() -> AsyncIterable[Item]:
    for item in items:
        yield item
```

## Server-Sent Events (SSE)

To stream Server-Sent Events, use `response_class=EventSourceResponse` and `yield` items from the endpoint.

Created: Sun Apr 05 07:19:11 GMT 2026

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github.com/tiangolo/fastapi

docs/en/docs/tutorial/stream-json-lines.md

///

### Non-async *path operation functions* { #non-async-path-operation-functions }

You can also use regular `def` functions (without `async`), and use `yield` the same way.

FastAPI will make sure it's run correctly so that it doesn't block the event loop.

As in this case the function is not async, the right return type would be `Iterable[Item]`:

Created: Sun Apr 05 07:19:11 GMT 2026

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github.com/tiangolo/fastapi

docs_src/request_files/tutorial002_an_py310.py

app = FastAPI()


@app.post("/files/")
async def create_files(files: Annotated[list[bytes], File()]):
    return {"file_sizes": [len(file) for file in files]}


@app.post("/uploadfiles/")
async def create_upload_files(files: list[UploadFile]):
    return {"filenames": [file.filename for file in files]}


@app.get("/")
async def main():
    content = """
<body>

Created: Sun Apr 05 07:19:11 GMT 2026

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