fastapi.exceptions.FastAPIError: Invalid args for response field! Hint: check that <class 'main.SoluteSolvent'> is a valid pydantic field type

Question

getting this error while executing the fast API code fastapi.exceptions.FastAPIError: Invalid args for response field: Hint. check that <class 'main.SoluteSolvent'> is a valid pydantic field type fastapi.exceptions.FastAPIError: Invalid args for response field: Hint. check that <class 'main.SoluteSolvent'> is a valid pydantic field type

class SoluteSolvent():
    solvent: Text
    solute: Text

response = {}
@app.get('/predict')
def predict(sol:SoluteSolvent):
    data = sol.dict()
    solute = data['solute']
    solvent = data['solvent']
    results = predictions(solute, solvent)
    print(results)
    response["predictions"] = results[0].item()
    response["interaction_map"] = (results[1].detach().numpy()).tolist()
    return {'result':response}

I was actually trying to replicate the code I have written for prediction in flask in fast API.

response = {}
@app.route('/predict', methods=["POST", "GET"])
def predict():
    if request.method=='POST':
        solute = request.form["solute"]
        solvent = request.form["solvent"]

    else:
        solute = request.args.get("solute")
        solvent = request.args.get("solvent")

    results = predictions(solute, solvent)
    
    response["predictions"] = results[0].item()
    response["interaction_map"] = (results[1].detach().numpy()).tolist()
    return flask.jsonify({'result': response})

Answer 1

The error says your type you pass to predict must be pydantic BaseModel (or dataclass from 0.67.0 version of FastApi). However it won't work that way (at least on get request), if you want to pass query params (suggested solution) list them in function:

@app.get('/predict')
def predict(solute: str, solvent: str):
   print(solute, solvent)

And use model for post request (which expects data in body):

from pydantic import BaseModel
class SoluteSolvent(BaseModel):
    solvent: str
    solute: str

@app.post('/predict')
def predict(sol:SoluteSolvent):
    print(sol.solute)

Or you can use underlying starlette Request directly

from fastapi import Request

async def predict(r: Request):
    print(r.query_params["solute"])