Problem rendering numpy.float32 through ORJSONRESPONSE

[yadavshashank]

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Code

from fastapi.responses import ORJSONResponse

app = FastAPI()

# Payload type
class Tweet(BaseModel):
    text: str

predict = Predict()

@app.get("/")
async def root():
    return {"message": "Hello World"}


@app.post("/sentiment", response_class=ORJSONResponse)
async def sentiment(tweet:Tweet):  
    data = predict.get_sentiment(tweet.text)

    # data contains the following keys
    # data = { "sentiment": type -> text, "polarity": type -> numpy.float32}
    return data

Description

I have exposed an endpoint which returns the sentiment of a text and its polarity (type ->numpy.float32).

This throws an error:

ERROR:    Exception in ASGI application
Traceback (most recent call last):
  File "c:\users\shash\anaconda3\envs\sentiment_analysis\lib\site-packages\uvicorn\protocols\http\h11_impl.py", line 388, in run_asgi
    result = await app(self.scope, self.receive, self.send)
  File "c:\users\shash\anaconda3\envs\sentiment_analysis\lib\site-packages\uvicorn\middleware\proxy_headers.py", line 45, in __call__
    return await self.app(scope, receive, send)
  File "c:\users\shash\anaconda3\envs\sentiment_analysis\lib\site-packages\fastapi\applications.py", line 183, in __call__
    await super().__call__(scope, receive, send)  # pragma: no cover
  File "c:\users\shash\anaconda3\envs\sentiment_analysis\lib\site-packages\starlette\applications.py", line 102, in __call__
    await self.middleware_stack(scope, receive, send)
  File "c:\users\shash\anaconda3\envs\sentiment_analysis\lib\site-packages\starlette\middleware\errors.py", line 181, in __call__
    raise exc from None
  File "c:\users\shash\anaconda3\envs\sentiment_analysis\lib\site-packages\starlette\middleware\errors.py", line 159, in __call__
    await self.app(scope, receive, _send)
  File "c:\users\shash\anaconda3\envs\sentiment_analysis\lib\site-packages\starlette\exceptions.py", line 82, in __call__
    raise exc from None
  File "c:\users\shash\anaconda3\envs\sentiment_analysis\lib\site-packages\starlette\exceptions.py", line 71, in __call__
    await self.app(scope, receive, sender)
  File "c:\users\shash\anaconda3\envs\sentiment_analysis\lib\site-packages\starlette\routing.py", line 550, in __call__
    await route.handle(scope, receive, send)
  File "c:\users\shash\anaconda3\envs\sentiment_analysis\lib\site-packages\starlette\routing.py", line 227, in handle
    await self.app(scope, receive, send)
  File "c:\users\shash\anaconda3\envs\sentiment_analysis\lib\site-packages\starlette\routing.py", line 41, in app
    response = await func(request)
  File "c:\users\shash\anaconda3\envs\sentiment_analysis\lib\site-packages\fastapi\routing.py", line 213, in app
    is_coroutine=is_coroutine,
  File "c:\users\shash\anaconda3\envs\sentiment_analysis\lib\site-packages\fastapi\routing.py", line 136, in serialize_response
    return jsonable_encoder(response_content)
  File "c:\users\shash\anaconda3\envs\sentiment_analysis\lib\site-packages\fastapi\encoders.py", line 115, in jsonable_encoder
    sqlalchemy_safe=sqlalchemy_safe,
  File "c:\users\shash\anaconda3\envs\sentiment_analysis\lib\site-packages\fastapi\encoders.py", line 160, in jsonable_encoder
    raise ValueError(errors)
ValueError: [TypeError("'numpy.float32' object is not iterable",), TypeError('vars() argument must have __dict__ attribute',)]

Additional comments

This does not occur if the value of polarity is typecast to float before returning the response.

Environment

• OS: Windows:
• FastAPI Version : 0.59.0
• Python version: 3.6.10

[phy25]

I don't think fastapi core is supposed to know how to convert numpy objects into a JSON-compatible object. You can define custom JSON encoder in the Pydantic model - #18

[SnkSynthesis]

@yadavshashank

You have to convert the numpy.float32 type to a python float type

so you can use the float() function

data['polarity'] = float(data['polarity'])

[yadavshashank]

@SnkSynthesis, as I mentioned, that is the workaround I used, thanks. Was wondering why it was happening.
@phy25, yes that might be another solution.

Could this be turned into a feature request? Would be helpful in future.

[IsaiahT-Tech]

@yadavshashank

orjson doesn't support serializing individual numpy data types yet. There is a pull request trying to implement that though.

[yadavshashank]

Thanks!

[tiangolo]

Thanks for the help here everyone! 👏 🙇

Thanks for reporting back and closing the issue 👍