Transmitir dados¶
🌐 Tradução por IA e humanos
Esta tradução foi feita por IA orientada por humanos. 🤝
Ela pode conter erros de interpretação do significado original ou soar pouco natural, etc. 🤖
Você pode melhorar esta tradução ajudando-nos a orientar melhor o LLM de IA.
Se você quer transmitir dados que podem ser estruturados como JSON, você deveria Transmitir JSON Lines.
Mas se você quer transmitir dados binários puros ou strings, veja como fazer.
Informação
Adicionado no FastAPI 0.134.0.
Casos de uso¶
Você pode usar isto para transmitir strings puras, por exemplo diretamente da saída de um serviço de AI LLM.
Você também pode usá-lo para transmitir arquivos binários grandes, enviando cada bloco de dados à medida que o lê, sem precisar carregar tudo na memória de uma vez.
Você também pode transmitir vídeo ou áudio desta forma; pode até ser gerado enquanto você processa e envia.
Um StreamingResponse com yield¶
Se você declarar response_class=StreamingResponse na sua função de operação de rota, você pode usar yield para enviar cada bloco de dados em sequência.
from collections.abc import AsyncIterable, Iterable
from fastapi import FastAPI
from fastapi.responses import StreamingResponse
app = FastAPI()
message = """
Rick: (stumbles in drunkenly, and turns on the lights) Morty! You gotta come on. You got--... you gotta come with me.
Morty: (rubs his eyes) What, Rick? What's going on?
Rick: I got a surprise for you, Morty.
Morty: It's the middle of the night. What are you talking about?
Rick: (spills alcohol on Morty's bed) Come on, I got a surprise for you. (drags Morty by the ankle) Come on, hurry up. (pulls Morty out of his bed and into the hall)
Morty: Ow! Ow! You're tugging me too hard!
Rick: We gotta go, gotta get outta here, come on. Got a surprise for you Morty.
"""
@app.get("/story/stream", response_class=StreamingResponse)
async def stream_story() -> AsyncIterable[str]:
for line in message.splitlines():
yield line
# Code below omitted 👇
👀 Full file preview
from collections.abc import AsyncIterable, Iterable
from fastapi import FastAPI
from fastapi.responses import StreamingResponse
app = FastAPI()
message = """
Rick: (stumbles in drunkenly, and turns on the lights) Morty! You gotta come on. You got--... you gotta come with me.
Morty: (rubs his eyes) What, Rick? What's going on?
Rick: I got a surprise for you, Morty.
Morty: It's the middle of the night. What are you talking about?
Rick: (spills alcohol on Morty's bed) Come on, I got a surprise for you. (drags Morty by the ankle) Come on, hurry up. (pulls Morty out of his bed and into the hall)
Morty: Ow! Ow! You're tugging me too hard!
Rick: We gotta go, gotta get outta here, come on. Got a surprise for you Morty.
"""
@app.get("/story/stream", response_class=StreamingResponse)
async def stream_story() -> AsyncIterable[str]:
for line in message.splitlines():
yield line
@app.get("/story/stream-no-async", response_class=StreamingResponse)
def stream_story_no_async() -> Iterable[str]:
for line in message.splitlines():
yield line
@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)
async def stream_story_bytes() -> AsyncIterable[bytes]:
for line in message.splitlines():
yield line.encode("utf-8")
@app.get("/story/stream-no-async-bytes", response_class=StreamingResponse)
def stream_story_no_async_bytes() -> Iterable[bytes]:
for line in message.splitlines():
yield line.encode("utf-8")
@app.get("/story/stream-no-annotation-bytes", response_class=StreamingResponse)
async def stream_story_no_annotation_bytes():
for line in message.splitlines():
yield line.encode("utf-8")
@app.get("/story/stream-no-async-no-annotation-bytes", response_class=StreamingResponse)
def stream_story_no_async_no_annotation_bytes():
for line in message.splitlines():
yield line.encode("utf-8")
O FastAPI entregará cada bloco de dados para StreamingResponse como está, não tentará convertê-lo para JSON nem nada semelhante.
Funções de operação de rota não assíncronas¶
Você também pode usar funções def normais (sem async) e usar yield da mesma forma.
# Code above omitted 👆
@app.get("/story/stream-no-async", response_class=StreamingResponse)
def stream_story_no_async() -> Iterable[str]:
for line in message.splitlines():
yield line
# Code below omitted 👇
👀 Full file preview
from collections.abc import AsyncIterable, Iterable
from fastapi import FastAPI
from fastapi.responses import StreamingResponse
app = FastAPI()
message = """
Rick: (stumbles in drunkenly, and turns on the lights) Morty! You gotta come on. You got--... you gotta come with me.
Morty: (rubs his eyes) What, Rick? What's going on?
Rick: I got a surprise for you, Morty.
Morty: It's the middle of the night. What are you talking about?
Rick: (spills alcohol on Morty's bed) Come on, I got a surprise for you. (drags Morty by the ankle) Come on, hurry up. (pulls Morty out of his bed and into the hall)
Morty: Ow! Ow! You're tugging me too hard!
Rick: We gotta go, gotta get outta here, come on. Got a surprise for you Morty.
"""
@app.get("/story/stream", response_class=StreamingResponse)
async def stream_story() -> AsyncIterable[str]:
for line in message.splitlines():
yield line
@app.get("/story/stream-no-async", response_class=StreamingResponse)
def stream_story_no_async() -> Iterable[str]:
for line in message.splitlines():
yield line
@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)
async def stream_story_bytes() -> AsyncIterable[bytes]:
for line in message.splitlines():
yield line.encode("utf-8")
@app.get("/story/stream-no-async-bytes", response_class=StreamingResponse)
def stream_story_no_async_bytes() -> Iterable[bytes]:
for line in message.splitlines():
yield line.encode("utf-8")
@app.get("/story/stream-no-annotation-bytes", response_class=StreamingResponse)
async def stream_story_no_annotation_bytes():
for line in message.splitlines():
yield line.encode("utf-8")
@app.get("/story/stream-no-async-no-annotation-bytes", response_class=StreamingResponse)
def stream_story_no_async_no_annotation_bytes():
for line in message.splitlines():
yield line.encode("utf-8")
Sem anotação¶
Você não precisa declarar a anotação de tipo de retorno para transmitir dados binários.
Como o FastAPI não tentará converter os dados para JSON com Pydantic nem serializá-los de nenhuma forma, neste caso a anotação de tipo serve apenas para seu editor e ferramentas; ela não será usada pelo FastAPI.
# Code above omitted 👆
@app.get("/story/stream-no-annotation", response_class=StreamingResponse)
async def stream_story_no_annotation():
for line in message.splitlines():
yield line
# Code below omitted 👇
👀 Full file preview
from collections.abc import AsyncIterable, Iterable
from fastapi import FastAPI
from fastapi.responses import StreamingResponse
app = FastAPI()
message = """
Rick: (stumbles in drunkenly, and turns on the lights) Morty! You gotta come on. You got--... you gotta come with me.
Morty: (rubs his eyes) What, Rick? What's going on?
Rick: I got a surprise for you, Morty.
Morty: It's the middle of the night. What are you talking about?
Rick: (spills alcohol on Morty's bed) Come on, I got a surprise for you. (drags Morty by the ankle) Come on, hurry up. (pulls Morty out of his bed and into the hall)
Morty: Ow! Ow! You're tugging me too hard!
Rick: We gotta go, gotta get outta here, come on. Got a surprise for you Morty.
"""
@app.get("/story/stream", response_class=StreamingResponse)
async def stream_story() -> AsyncIterable[str]:
for line in message.splitlines():
yield line
@app.get("/story/stream-no-async", response_class=StreamingResponse)
def stream_story_no_async() -> Iterable[str]:
for line in message.splitlines():
yield line
@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)
async def stream_story_bytes() -> AsyncIterable[bytes]:
for line in message.splitlines():
yield line.encode("utf-8")
@app.get("/story/stream-no-async-bytes", response_class=StreamingResponse)
def stream_story_no_async_bytes() -> Iterable[bytes]:
for line in message.splitlines():
yield line.encode("utf-8")
@app.get("/story/stream-no-annotation-bytes", response_class=StreamingResponse)
async def stream_story_no_annotation_bytes():
for line in message.splitlines():
yield line.encode("utf-8")
@app.get("/story/stream-no-async-no-annotation-bytes", response_class=StreamingResponse)
def stream_story_no_async_no_annotation_bytes():
for line in message.splitlines():
yield line.encode("utf-8")
Isso também significa que, com StreamingResponse, você tem a liberdade e a responsabilidade de produzir e codificar os bytes exatamente como precisam ser enviados, independentemente das anotações de tipo. 🤓
Transmitir bytes¶
Um dos principais casos de uso é transmitir bytes em vez de strings; você pode fazer isso sem problemas.
# Code above omitted 👆
@app.get("/story/stream-bytes", response_class=StreamingResponse)
async def stream_story_bytes() -> AsyncIterable[bytes]:
for line in message.splitlines():
yield line.encode("utf-8")
# Code below omitted 👇
👀 Full file preview
from collections.abc import AsyncIterable, Iterable
from fastapi import FastAPI
from fastapi.responses import StreamingResponse
app = FastAPI()
message = """
Rick: (stumbles in drunkenly, and turns on the lights) Morty! You gotta come on. You got--... you gotta come with me.
Morty: (rubs his eyes) What, Rick? What's going on?
Rick: I got a surprise for you, Morty.
Morty: It's the middle of the night. What are you talking about?
Rick: (spills alcohol on Morty's bed) Come on, I got a surprise for you. (drags Morty by the ankle) Come on, hurry up. (pulls Morty out of his bed and into the hall)
Morty: Ow! Ow! You're tugging me too hard!
Rick: We gotta go, gotta get outta here, come on. Got a surprise for you Morty.
"""
@app.get("/story/stream", response_class=StreamingResponse)
async def stream_story() -> AsyncIterable[str]:
for line in message.splitlines():
yield line
@app.get("/story/stream-no-async", response_class=StreamingResponse)
def stream_story_no_async() -> Iterable[str]:
for line in message.splitlines():
yield line
@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)
async def stream_story_bytes() -> AsyncIterable[bytes]:
for line in message.splitlines():
yield line.encode("utf-8")
@app.get("/story/stream-no-async-bytes", response_class=StreamingResponse)
def stream_story_no_async_bytes() -> Iterable[bytes]:
for line in message.splitlines():
yield line.encode("utf-8")
@app.get("/story/stream-no-annotation-bytes", response_class=StreamingResponse)
async def stream_story_no_annotation_bytes():
for line in message.splitlines():
yield line.encode("utf-8")
@app.get("/story/stream-no-async-no-annotation-bytes", response_class=StreamingResponse)
def stream_story_no_async_no_annotation_bytes():
for line in message.splitlines():
yield line.encode("utf-8")
Um PNGStreamingResponse personalizado¶
Nos exemplos acima, os bytes eram transmitidos, mas a resposta não tinha um cabeçalho Content-Type, então o cliente não sabia que tipo de dado estava recebendo.
Você pode criar uma subclasse personalizada de StreamingResponse que define o cabeçalho Content-Type para o tipo de dado que você está transmitindo.
Por exemplo, você pode criar um PNGStreamingResponse que define o cabeçalho Content-Type como image/png usando o atributo media_type:
# Code above omitted 👆
from fastapi.responses import StreamingResponse
# Code here omitted 👈
class PNGStreamingResponse(StreamingResponse):
media_type = "image/png"
# Code below omitted 👇
👀 Full file preview
import base64
from collections.abc import AsyncIterable, Iterable
from io import BytesIO
from fastapi import FastAPI
from fastapi.responses import StreamingResponse
image_base64 = "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"
binary_image = base64.b64decode(image_base64)
def read_image() -> BytesIO:
return BytesIO(binary_image)
app = FastAPI()
class PNGStreamingResponse(StreamingResponse):
media_type = "image/png"
@app.get("/image/stream", response_class=PNGStreamingResponse)
async def stream_image() -> AsyncIterable[bytes]:
with read_image() as image_file:
for chunk in image_file:
yield chunk
@app.get("/image/stream-no-async", response_class=PNGStreamingResponse)
def stream_image_no_async() -> Iterable[bytes]:
with read_image() as image_file:
for chunk in image_file:
yield chunk
@app.get("/image/stream-no-async-yield-from", response_class=PNGStreamingResponse)
def stream_image_no_async_yield_from() -> Iterable[bytes]:
with read_image() as image_file:
yield from image_file
@app.get("/image/stream-no-annotation", response_class=PNGStreamingResponse)
async def stream_image_no_annotation():
with read_image() as image_file:
for chunk in image_file:
yield chunk
@app.get("/image/stream-no-async-no-annotation", response_class=PNGStreamingResponse)
def stream_image_no_async_no_annotation():
with read_image() as image_file:
for chunk in image_file:
yield chunk
Em seguida, você pode usar essa nova classe em response_class=PNGStreamingResponse na sua função de operação de rota:
# Code above omitted 👆
@app.get("/image/stream", response_class=PNGStreamingResponse)
async def stream_image() -> AsyncIterable[bytes]:
with read_image() as image_file:
for chunk in image_file:
yield chunk
# Code below omitted 👇
👀 Full file preview
import base64
from collections.abc import AsyncIterable, Iterable
from io import BytesIO
from fastapi import FastAPI
from fastapi.responses import StreamingResponse
image_base64 = "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"
binary_image = base64.b64decode(image_base64)
def read_image() -> BytesIO:
return BytesIO(binary_image)
app = FastAPI()
class PNGStreamingResponse(StreamingResponse):
media_type = "image/png"
@app.get("/image/stream", response_class=PNGStreamingResponse)
async def stream_image() -> AsyncIterable[bytes]:
with read_image() as image_file:
for chunk in image_file:
yield chunk
@app.get("/image/stream-no-async", response_class=PNGStreamingResponse)
def stream_image_no_async() -> Iterable[bytes]:
with read_image() as image_file:
for chunk in image_file:
yield chunk
@app.get("/image/stream-no-async-yield-from", response_class=PNGStreamingResponse)
def stream_image_no_async_yield_from() -> Iterable[bytes]:
with read_image() as image_file:
yield from image_file
@app.get("/image/stream-no-annotation", response_class=PNGStreamingResponse)
async def stream_image_no_annotation():
with read_image() as image_file:
for chunk in image_file:
yield chunk
@app.get("/image/stream-no-async-no-annotation", response_class=PNGStreamingResponse)
def stream_image_no_async_no_annotation():
with read_image() as image_file:
for chunk in image_file:
yield chunk
Simular um arquivo¶
Neste exemplo, estamos simulando um arquivo com io.BytesIO, que é um objeto semelhante a arquivo que vive somente na memória, mas nos permite usar a mesma interface.
Por exemplo, podemos iterar sobre ele para consumir seu conteúdo, como faríamos com um arquivo.
import base64
from collections.abc import AsyncIterable, Iterable
from io import BytesIO
from fastapi import FastAPI
from fastapi.responses import StreamingResponse
image_base64 = "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"
binary_image = base64.b64decode(image_base64)
def read_image() -> BytesIO:
return BytesIO(binary_image)
app = FastAPI()
class PNGStreamingResponse(StreamingResponse):
media_type = "image/png"
@app.get("/image/stream", response_class=PNGStreamingResponse)
async def stream_image() -> AsyncIterable[bytes]:
with read_image() as image_file:
for chunk in image_file:
yield chunk
# Code below omitted 👇
👀 Full file preview
import base64
from collections.abc import AsyncIterable, Iterable
from io import BytesIO
from fastapi import FastAPI
from fastapi.responses import StreamingResponse
image_base64 = "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"
binary_image = base64.b64decode(image_base64)
def read_image() -> BytesIO:
return BytesIO(binary_image)
app = FastAPI()
class PNGStreamingResponse(StreamingResponse):
media_type = "image/png"
@app.get("/image/stream", response_class=PNGStreamingResponse)
async def stream_image() -> AsyncIterable[bytes]:
with read_image() as image_file:
for chunk in image_file:
yield chunk
@app.get("/image/stream-no-async", response_class=PNGStreamingResponse)
def stream_image_no_async() -> Iterable[bytes]:
with read_image() as image_file:
for chunk in image_file:
yield chunk
@app.get("/image/stream-no-async-yield-from", response_class=PNGStreamingResponse)
def stream_image_no_async_yield_from() -> Iterable[bytes]:
with read_image() as image_file:
yield from image_file
@app.get("/image/stream-no-annotation", response_class=PNGStreamingResponse)
async def stream_image_no_annotation():
with read_image() as image_file:
for chunk in image_file:
yield chunk
@app.get("/image/stream-no-async-no-annotation", response_class=PNGStreamingResponse)
def stream_image_no_async_no_annotation():
with read_image() as image_file:
for chunk in image_file:
yield chunk
Detalhes Técnicos
As outras duas variáveis, image_base64 e binary_image, são uma imagem codificada em Base64 e depois convertida para bytes, para então passá-la para io.BytesIO.
Apenas para que possa viver no mesmo arquivo deste exemplo e você possa copiar e executar como está. 🥚
Ao usar um bloco with, garantimos que o objeto semelhante a arquivo seja fechado após a função geradora (a função com yield) terminar. Ou seja, após terminar de enviar a resposta.
Isso não seria tão importante neste exemplo específico porque é um arquivo falso em memória (com io.BytesIO), mas com um arquivo real, seria importante garantir que o arquivo fosse fechado ao final do trabalho.
Arquivos e async¶
Na maioria dos casos, objetos semelhantes a arquivo não são compatíveis com async e await por padrão.
Por exemplo, eles não têm await file.read(), nem async for chunk in file.
E, em muitos casos, lê-los seria uma operação bloqueante (que poderia bloquear o loop de eventos), pois são lidos do disco ou da rede.
Informação
O exemplo acima é, na verdade, uma exceção, porque o objeto io.BytesIO já está em memória, então lê-lo não bloqueará nada.
Mas, em muitos casos, ler um arquivo ou um objeto semelhante a arquivo bloquearia.
Para evitar bloquear o loop de eventos, você pode simplesmente declarar a função de operação de rota com def normal em vez de async def. Assim, o FastAPI a executará em um worker de threadpool, evitando bloquear o loop principal.
# Code above omitted 👆
@app.get("/image/stream-no-async", response_class=PNGStreamingResponse)
def stream_image_no_async() -> Iterable[bytes]:
with read_image() as image_file:
for chunk in image_file:
yield chunk
# Code below omitted 👇
👀 Full file preview
import base64
from collections.abc import AsyncIterable, Iterable
from io import BytesIO
from fastapi import FastAPI
from fastapi.responses import StreamingResponse
image_base64 = "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"
binary_image = base64.b64decode(image_base64)
def read_image() -> BytesIO:
return BytesIO(binary_image)
app = FastAPI()
class PNGStreamingResponse(StreamingResponse):
media_type = "image/png"
@app.get("/image/stream", response_class=PNGStreamingResponse)
async def stream_image() -> AsyncIterable[bytes]:
with read_image() as image_file:
for chunk in image_file:
yield chunk
@app.get("/image/stream-no-async", response_class=PNGStreamingResponse)
def stream_image_no_async() -> Iterable[bytes]:
with read_image() as image_file:
for chunk in image_file:
yield chunk
@app.get("/image/stream-no-async-yield-from", response_class=PNGStreamingResponse)
def stream_image_no_async_yield_from() -> Iterable[bytes]:
with read_image() as image_file:
yield from image_file
@app.get("/image/stream-no-annotation", response_class=PNGStreamingResponse)
async def stream_image_no_annotation():
with read_image() as image_file:
for chunk in image_file:
yield chunk
@app.get("/image/stream-no-async-no-annotation", response_class=PNGStreamingResponse)
def stream_image_no_async_no_annotation():
with read_image() as image_file:
for chunk in image_file:
yield chunk
Dica
Se você precisar chamar código bloqueante de dentro de uma função assíncrona ou uma função assíncrona de dentro de uma função bloqueante, você poderia usar o Asyncer, uma biblioteca irmã do FastAPI.
yield from¶
Quando você está iterando sobre algo, como um objeto semelhante a arquivo, e faz yield para cada item, você também pode usar yield from para produzir cada item diretamente e pular o loop for.
Isso não é particular do FastAPI, é apenas Python, mas é um truque útil para conhecer. 😎
# Code above omitted 👆
@app.get("/image/stream-no-async-yield-from", response_class=PNGStreamingResponse)
def stream_image_no_async_yield_from() -> Iterable[bytes]:
with read_image() as image_file:
yield from image_file
# Code below omitted 👇
👀 Full file preview
import base64
from collections.abc import AsyncIterable, Iterable
from io import BytesIO
from fastapi import FastAPI
from fastapi.responses import StreamingResponse
image_base64 = "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"
binary_image = base64.b64decode(image_base64)
def read_image() -> BytesIO:
return BytesIO(binary_image)
app = FastAPI()
class PNGStreamingResponse(StreamingResponse):
media_type = "image/png"
@app.get("/image/stream", response_class=PNGStreamingResponse)
async def stream_image() -> AsyncIterable[bytes]:
with read_image() as image_file:
for chunk in image_file:
yield chunk
@app.get("/image/stream-no-async", response_class=PNGStreamingResponse)
def stream_image_no_async() -> Iterable[bytes]:
with read_image() as image_file:
for chunk in image_file:
yield chunk
@app.get("/image/stream-no-async-yield-from", response_class=PNGStreamingResponse)
def stream_image_no_async_yield_from() -> Iterable[bytes]:
with read_image() as image_file:
yield from image_file
@app.get("/image/stream-no-annotation", response_class=PNGStreamingResponse)
async def stream_image_no_annotation():
with read_image() as image_file:
for chunk in image_file:
yield chunk
@app.get("/image/stream-no-async-no-annotation", response_class=PNGStreamingResponse)
def stream_image_no_async_no_annotation():
with read_image() as image_file:
for chunk in image_file:
yield chunk