how to pass parameter from POST method and do function call in flask?

Question

In flask-restplus , or alternatively flask , I want to call my custom function which is called by POST request, where POST method passes the parameter to a custom function, then function take a parameter and do calculation then returns the output to the server endpoint. I am not quite sure how to make this happen, but the whole picture of the process I kinda get it. Can anyone show me how to do this? Is there any way to do this in flask or flask-restplus ? any thought?

minimal flask app

here is the minimal flask app that I wrote:

from flask import Flask, jsonify
from flask_restplus import Api, Resource, fields, reqparse, inputs

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

payload = api.model('Payload', {
    'num': fields.Integer(required=True)
})


@ns.route('/')
class AResource(Resource):
    @ns.expect(payload)
    def post(self):
        parser = reqparse.RequestParser()
        parser.add_argument('num', type=str, required=True)
        try:  # Will raise an error if date can't be parsed.
            args = parser.parse_args()
            param = args['num]  ## todo: how to pass params to my custom function
            ## output from custom function, where function would consum param
            return jsonify(output)
        except:
            return None, 400

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

custom function

here is the custom function that POST method is going to call and trigger the function to run and return its output to server endpoint:

primest <- function(num){
  p <- 2:num
  i <- 1
  while (p[i] <= sqrt(num)) {
    p <-  p[p %% p[i] != 0 | p==p[i]]
    i <- i+1
  }
  p
}

update

whenever api post method is used, post method will pass the parameter to custom function then custom function will do a calculation and return its output as json object to the server endpoint. how to elaborate this process easier? any thought?

and I can call R function from python using this:

@ns.route('/')
class Rsession(Resource):
    def get(self):
        output = subprocess.call(['Rscript','--vanilla','-e','primest.R'])
        return {'call function': output}

I got stuck how am I gonna pass and parse argument in order to call my custom function. How to make this happen in flask or flask-restplus? any possible thought? how can I call a function which is called by POST request? any idea?

Answer 1

as far as I understood your question correctly, you just made things complicated. instead of using arg_parse , let's do like this:

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

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

payload = api.model('Payload', {
    'num': fields.Integer(required=True)
})

@api.route('/')
class AResource(Resource):
    @ns.expect(payload)
    def post(self):
        param = request.json['num']
        try: 
            res = primes_method1(param)
            return jsonify(res)
        except:
            return None, 400

def primes_method1(n):
    out = list()
    for num in range(1, n+1):
        prime = True
        for i in range(2, num):
            if (num % i == 0):
                prime = False
        if prime:
            out.append(num)
    return out


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

this solution is totally working fine for me, hope would resolve your doubt. If you want to call R function from python, subprocess.call() would do the jobs. hope this is what you want.