@app.get("/story/stream-no-annotation", response_class=StreamingResponse)
async def stream_story_no_annotation():
    for line in message.splitlines():
        yield line


@app.get("/story/stream-no-async-no-annotation", response_class=StreamingResponse)
def stream_story_no_async_no_annotation():
    for line in message.splitlines():
        yield line


@app.get("/story/stream-bytes", response_class=StreamingResponse)

```

## Stream bytes

To stream bytes, declare a `response_class=` of `StreamingResponse` or a sub-class, and use `yield` to return the data.

```python
from fastapi import FastAPI
from fastapi.responses import StreamingResponse
from app.utils import read_image

app = FastAPI()


class PNGStreamingResponse(StreamingResponse):
    media_type = "image/png"

@app.get("/image", response_class=PNGStreamingResponse)

    def iter_data():
        yield json.dumps({"is_open": session.open})

    return StreamingResponse(iter_data())


@app.get("/request-scope")
def request_scope(session: SessionRequestDep) -> Any:
    def iter_data():
        yield json.dumps({"is_open": session.open})

    return StreamingResponse(iter_data())


@app.get("/two-scopes")
def get_stream_session(

def get_stream_simple(session: SessionDep) -> Any:
    def iter_data():
        yield from ["x", "y", "z"]

    return StreamingResponse(iter_data())


@app.get("/stream-session")
def get_stream_session(session: SessionDep) -> Any:
    def iter_data():
        yield from session

    return StreamingResponse(iter_data())


@app.get("/broken-session-data")
def get_broken_session_data(session: BrokenSessionDep) -> Any:

## A `StreamingResponse` with `yield` { #a-streamingresponse-with-yield }

If you declare a `response_class=StreamingResponse` in your *path operation function*, you can use `yield` to send each chunk of data in turn.

{* ../../docs_src/stream_data/tutorial001_py310.py ln[1:23] hl[20,23] *}

import base64
from collections.abc import AsyncIterable, Iterable
from io import BytesIO

from fastapi import FastAPI
from fastapi.responses import StreamingResponse

你也可以用它来流式传输大型二进制文件，在读取的同时按块发送，无需一次性把所有内容读入内存。

你还可以用这种方式流式传输视频或音频，甚至可以在处理的同时生成并发送。

## 使用 `yield` 的 `StreamingResponse` { #a-streamingresponse-with-yield }

如果你在*路径操作函数*中声明 `response_class=StreamingResponse`，你就可以使用 `yield` 依次发送每个数据块。

{* ../../docs_src/stream_data/tutorial001_py310.py ln[1:23] hl[20,23] *}

FastAPI 会将每个数据块原样交给 `StreamingResponse`，不会尝试将其转换为 JSON 或做类似处理。

### 非 async 的*路径操作函数* { #non-async-path-operation-functions }

import time
from typing import Annotated

from fastapi import Depends, FastAPI, HTTPException
from fastapi.responses import StreamingResponse
from sqlmodel import Field, Session, SQLModel, create_engine

engine = create_engine("postgresql+psycopg://postgres:postgres@localhost/db")


class User(SQLModel, table=True):
    id: int | None = Field(default=None, primary_key=True)
    name: str


app = FastAPI()


def get_session():

import time
from typing import Annotated

from fastapi import Depends, FastAPI, HTTPException
from fastapi.responses import StreamingResponse
from sqlmodel import Field, Session, SQLModel, create_engine

engine = create_engine("postgresql+psycopg://postgres:postgres@localhost/db")


class User(SQLModel, table=True):
    id: int | None = Field(default=None, primary_key=True)
    name: str


app = FastAPI()


def get_session():

同様に、動画や音声をストリームすることもできます。処理しながら生成し、そのまま送信することも可能です。

## `yield` を使った `StreamingResponse` { #a-streamingresponse-with-yield }

path operation 関数で `response_class=StreamingResponse` を宣言すると、`yield` を使ってデータをチャンクごとに順次送信できます。

{* ../../docs_src/stream_data/tutorial001_py310.py ln[1:23] hl[20,23] *}

FastAPI は各データチャンクをそのまま `StreamingResponse` に渡し、JSON などに変換しようとはしません。