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Responses

Default Response

By default, FastAPI will return the responses using JSONResponse

  • automatically convert that return value to JSON using the jsonable_encoder

Custom Response

Returning a Response

Example of returning XML as a custom Response

from fastapi import FastAPI, Response

app = FastAPI()

@app.get("/legacy/")
def get_legacy_data():
  data = """<?xml version="1.0"?>
  <shampoo>
  <Header>
      Apply shampoo here.
  </Header>
  <Body>
      You'll have to use soap here.
  </Body>
  </shampoo>
  """
  return Response(content=data, media_type="application/xml")

ORJSONResponse

Installation

pip3 install --upgrade orjson

HTTP header Content-Type will be set to application/json

from fastapi import FastAPI
from fastapi.responses import ORJSONResponse

app = FastAPI()

@app.get("/items/", response_class=ORJSONResponse)
async def read_items():
  return ORJSONResponse([{"item_id": "Foo"}])

HTMLResponse

from fastapi import FastAPI
from fastapi.responses import HTMLResponse

app = FastAPI()

@app.get("/items/", response_class=HTMLResponse)
async def read_items():
  return """
  <html>
    <head>
      <title>Some HTML in here</title>
    </head>
    <body>
      <h1>Look ma! HTML!</h1>
    </body>
  </html>
  """

RedirectResponse

from fastapi import FastAPI
from fastapi.responses import RedirectResponse

app = FastAPI()

@app.get("/typer")
async def redirect_typer():
  return RedirectResponse("https://typer.tiangolo.com")

StreamingResponse

from fastapi import FastAPI
from fastapi.responses import StreamingResponse

app = FastAPI()

async def fake_video_streamer():
  for i in range(10):
    yield b"some fake video bytes"

@app.get("/")
async def main():
  return StreamingResponse(fake_video_streamer())

# Use with file-like objects
from fastapi import FastAPI
from fastapi.responses import StreamingResponse

some_file_path = "large-video-file.mp4"
app = FastAPI()


@app.get("/")
def main():
  # yield = generator function
  def iterfile(): 
    # with closes the file-like object after generator function is done
    with open(some_file_path, mode="rb") as file_like:
      yield from file_like

  return StreamingResponse(iterfile(), media_type="video/mp4")
© VincentVanKoh