fastapi post request : getting null instead of numpy array

Question

I am trying to run this code from a directory, C:\users\user1\plant_app\main.py Edit: I am able to start the server, but I can't get the numpy array.

from fastapi import FastAPI, File, UploadFile
import uvicorn
from io import BytesIO
import numpy as np
from PIL import Image


def read_image(data):
    return np.array(Image.open(BytesIO(data)))

app=FastAPI()
@app.get('/check')
async def check():
     return {'message':'hello world'}
@app.post('/predict')
async def predict(file: UploadFile = File(...)):
     image=read_image(await file.read())
     return image


if __name__=='__main__':
    uvicorn.run(app,host='localhost',port=8000)

I am getting this error.

PS C:\Users\user1\plant_app> python -u "c:\Users\user1\plant_app\main.py"
INFO:     Started server process [21740]
INFO:     Waiting for application startup.
INFO:     Application startup complete.
INFO:     Uvicorn running on http://localhost:8000 (Press CTRL+C to quit)
INFO:     127.0.0.1:58115 - "GET / HTTP/1.1" 404 Not Found

What am I doing wrong here?

Answer 1

@app.get('/')
dуf root():
    return {'message':'FastAPI app'}

you should define / url

Answer 2

@app.get('/')
async def root():
    return {'message': 'test'}

Try adding this because it seems like the GET route to '/' hasn't been declared.

Answer 3

We can access the API from http://localhost:8000/check or http://localhost:8000/predict. Or we can also use SwaggerUI which is integrated with FastAPI to interact with API.

Answer 4

Try this. I think the problem is returning the image. You need to create a response with a type of image (here image/png as my test case was a png file). I wasn't sure of what output you wanted. So, I made three services: one returns the np array, the other returns the shape of the array, and finally the one returns the image itself. Check the following links for more info:

• get bytes from upload: How to upload File in FastAPI, then to Amazon S3 and finally process it?
• return np array in a service: How can I return a NumPy array using FastAPI?
• return an image in a service: How do I return an image in fastAPI?

from fastapi import FastAPI, File, UploadFile
import uvicorn
from io import BytesIO
import numpy as np
from PIL import Image
from fastapi.responses import Response
import json

def read_image(data):
    return np.array(Image.open(BytesIO(data)))

app=FastAPI()

@app.get('/')
async def check():
     return {'message':'hello world'}


@app.post('/array')
async def predict_array(file: UploadFile = File(...)):
     content = await file.read()
     image = read_image(content)
     return json.dumps(image.tolist())


@app.post('/shape')
async def predict_shape(file: UploadFile = File(...)):
     content = await file.read()
     image = read_image(content)
     return {'shape': image.shape}

@app.post('/image')
async def return_image(file: UploadFile = File(...)):
     content = await file.read()
     return Response(content=content, media_type="image/png")

if __name__=='__main__':
    uvicorn.run(app,host='localhost', port=8000)

Answer 5

The error you are encountering indicates that the route you are trying to access is not found. In your code, you have defined two routes: /check and /predict. However, when you make a GET request to the root URL http://localhost:8000/, it returns a 404 Not Found error because you haven't defined a route for the root URL.

To fix this issue, you can add a route for the root URL / in your FastAPI application.

from fastapi import FastAPI, File, UploadFile
import uvicorn
from io import BytesIO
import numpy as np
from PIL import Image


def read_image(data):
    return np.array(Image.open(BytesIO(data)))


app = FastAPI()


@app.get('/')
async def root():
    return {'message': 'Welcome to the API'}


@app.get('/check')
async def check():
    return {'message': 'Hello, world'}


@app.post('/predict')
async def predict(file: UploadFile = File(...)):
    image = read_image(await file.read())
    # Perform your prediction or processing here using the image
    # Return the result or perform further actions as needed
    return {'message': 'Prediction successful', 'image_shape': image.shape}


if __name__ == '__main__':
    uvicorn.run(app, host='localhost', port=8000)

In this updated code, the root URL / is defined with the @app.get('/') decorator, and it returns a simple welcome message. Now, when you access http://localhost:8000/, you should see the response from the root route.

Additionally, I uncommented the code inside the /predict route so that it reads the uploaded image, converts it to a NumPy array, and performs further processing or prediction tasks as required.