Can't return dictionary as response when values are numpy arrays

from backend import Model
from fastapi import FastAPI, File, Form, UploadFile

app = FastAPI()
model = Model()

@app.get("/")
def read_root():
    return {"Hello World"}

@app.post("/enroll")
def enroll_user(uploadedfile: UploadFile = File(...), username: str = Form(...)):
    model.enroll(uploadedfile.file, username)
    return "success"

@app.get("/db")
def view_db():
    return model._database

Description

• I receive an uploaded audio file and a username and pass them to model.enroll to generate an embedding for that file and store it in the dictionary _database as `{username: embedding}.
• Embedding is of type numpy.ndarray and of shape (1, 512).
• The problem arises when I try and hit the /db endpoint to view the _database variable, it works when the dictionary is still empty but when it is populated it throws back this error ValueError: [ValueError('dictionary update sequence element #0 has length 512; 2 is required'), TypeError('vars() argument must have __dict__ attribute')].
• The error seems to arise from fastapi/encoders line 139.
• I tried populating the dictionary with all sorts of sequences and it worked just fine.
• The expected return is {username: embedding}.

Environment

• OS: Linux
• FastAPI Version: 0.61.1
• Python version: 3.8.2

[Mause]

It looks like fastapi is trying to fall back to converting the numpy array to a dict using vars as it doesn’t know what to do with it. You are probably best off converting the array into a python list yourself before returning it.

@app.get("/db")
def view_db():
    return {username: embedding.tolist() for username, embedding in model._database.items()}

[tiangolo]

Thanks for the help everyone! ☕

And thanks for coming back to close the issue @kareemamrr 🍰

Sorry for the long delay! 🙈 I wanted to personally address each issue/PR and they piled up through time, but now I’m checking each one in order.