can't fix error: Object of type ListVector is not JSON serializable on flask?

Question

I am trying to make a request for session info, and I could print out session info on python console, but can't return session info on server endpoint. The error said the object is not JSON serializable. Here is the error message:

TypeError: Object of type ListVector is not JSON serializable

I found this post relevant to my post, I tried its solution, but it didn't work for me. how can I convert rpy2.ListVector to the dictionary that can be JSON serializable? any solution?

my attempt:

from flask import Flask, jsonify, request
from flask_restplus import Api, Resource
import json

##
import os

os.environ['PYTHONHOME'] = r"C:\Users\me\AppData\Local\Programs\Python\Python37"
os.environ['PYTHONPATH'] = r"C:\Users\me\AppData\Local\Programs\Python\Python37\Lib\site-packages"
os.environ['R_HOME'] = r"C:\Program Files\R\R-3.3.2"
os.environ['R_USER'] = r"C:\Users\me\AppData\Local\Programs\Python\Python37\Lib\site-packages\rpy2"
##

app = Flask(__name__)
api = Api(app)
ns = api.namespace('ns')

## load R function
import rpy2
import rpy2.robjects as robjects
@api.route('/')
class AResource(Resource):
    def post(self):
        sess = robjects.r("sessionInfo()")
        return jsonify({'sessioninfo': sess})

if __name__ == '__main__':
    api.add_namespace(ns)
    app.run(debug=True)

here I just simply make a request to the server endpoint, I can print out session info on console but not able to return it on server endpoint. how can I make this work? any quick thought? thanks

Is there any possible solution to fix this error? any idea?

Answer 1

follow up your above attempt, I fixed your problem as follow:

class AResource(Resource):
    def post(self):
        sess = robjects.r("sessionInfo()")
        new_sess= { key : sess.rx2(key)[0] for key in sess.names }
        return jsonify({'sessioninfo': str(new_sess)})

now you can see json output on your server endpoint.