TypeError: Object of type builtin_function_or_method is not JSON serializable

Question

This is my first time working on webserver, and I'm writing restful get request using flask to pass parameters to the predictive model that I built.

from flask import Flask, Response


app = Flask(__name__)
api = Api(app)

class AST(Resource):
    def get(self):
        args = request.args
        x1 = args['key1']
        x2 = args['key2']
        X = [[x1, x2]]
        x = load_scaler.transform(X)
        y_predict = load_model.predict(x)
        y_predict = load_model.predict(np.array(x)).tolist
        time = [{'predection':y_predict}]
        return Response (json.dumps(time),  mimetype='application/json')


api.add_resource(AST, '/start_time')

if __name__ == '__main__':
    app.run

When I ran the code, it gave me the error:

TypeError: Object of type builtin_function_or_method is not JSON serializable

The traceback shows

File "/Users/123/Documents/123/webserver/predictionast.py", line 60, in get
    return Response (json.dumps(time),  mimetype='application/json')
  File "/Users/123/opt/anaconda3/lib/python3.7/json/__init__.py", line 231, in dumps
    return _default_encoder.encode(obj)
  File "/Users/123/opt/anaconda3/lib/python3.7/json/encoder.py", line 199, in encode
    chunks = self.iterencode(o, _one_shot=True)
  File "/Users/123/opt/anaconda3/lib/python3.7/json/encoder.py", line 257, in iterencode
    return _iterencode(o, 0)
  File "/Users/123/opt/anaconda3/lib/python3.7/json/encoder.py", line 179, in default
    raise TypeError(f'Object of type {o.__class__.__name__} '
TypeError: Object of type builtin_function_or_method is not JSON serializable

y_predict is array

Answer 1

This error as says "object of built in types are not JSON serializable" occurs when you try to pass python built in method or attributes to the json.loads or dumps methods. It fails to serialize the internal types of python methods. For example:

json_1 = {"time": datetime.now}
json_2 = {"time": str(datetime.now)}
print(json.loads(json_2))
print(json.loads(json_1))

The json_1 object will fail when you try to print it while serialzing as it uses the internal bulit in python method. On the other hand the json_2 would be serialized and printed as it uses the well known data type to JSON - String.