How to trigger a REST API based on a condition in Flask?

I have a Flask application where I let users access third party applications and fetch data from them and perform some visualizations.Now the user has to provide the application name and it's credentials in order to fetch the data.Now I want to avoid putting the application name in the url and rather all of the data should be sent as a POST request where I will parse the POST data, connect to the required app with the given credentials and perform some visualizations.This is what the user will send as a POST data

{
    "application_name": "appdynamics",
    "account_id": "sdf632sef",
    "username": "kuhku86tg",
    "password": "oihsd832"
}

Now I want to trigger my particular REST API class based on the application name provided by the user.

The way I planned was to create a seperate file that involves getting the POST data using request parser and then calling it in the main application where I will trigger my REST API class with a if condition based on the application name.Below is the file parse.py

from flask_restful import reqparse

# create a parser object
parser = reqparse.RequestParser()
# add agruments to the parser object
parser.add_argument('account_id', type=str, required=False, help="Please define 'account_id'")
parser.add_argument('username', type=str, required=False, help="Please define 'username'")
parser.add_argument('password', type=str, required=False, help="Please define 'password'")
parser.add_argument('application_name', type=str, required=False, help="Please define 'application name'")

data = parser.parse_args()

Now I call it in the main application app.py

from parser import data
from flask import Flask
from flask_restful import Api

app = Flask(__name__)
# create an API for the Flask app
api = Api(app)

# if the user demands info for appdynamics, trigger the Appdynamics API class
if data['application_name'] == "appdynamics":
    api.add_resource(AppdynamicsAPI, "/<string:name>")  # the string will contain the metric requirement

if __name__ == "__main__":
    app.run(port=5000, debug=True)

Below is the section where the logic for the REST API is written

from parser import data
from flask_restful import Resource, reqparse
from fetch_data.appdynamics import fetch_all_apps, fetch_avg_resp_time, calls_per_min
from models.user import *

class AppdynamicsAPI(Resource):
    # authenticate users
    def post(self, name):
        first_data = data
        # if the user passes the credentials, insert it into the database otherwise use the last known credentials
        # ensure you only insert valid credentials
        if all([first_data['account_id'], first_data['password'], first_data['username']]):
            users.update(first_data, {i: j for i, j in first_data.items()}, upsert=True)
            print({i: j for i, j in first_data.items()})
        credentials = users.find_one({})
        print("Credentials", credentials)
        account_id = credentials['account_id']
        username = credentials['username']
        password = credentials['password']
        t_duration = first_data['t_duration']


        if name == "allapps":
            status_code, result = fetch_all_apps(account_id, username, password)
            if status_code == 200:
                return {"information": result}, status_code
            return {"message": "Please enter correct credentials"}, status_code

However I receive the below error

    Traceback (most recent call last):
  File "/home/souvik/PycharmProjects/ServiceHandler/app.py", line 3, in <module>
    from resource.appdynamics_resource import AppdynamicsAPI
  File "/home/souvik/PycharmProjects/ServiceHandler/resource/appdynamics_resource.py", line 4, in <module>
    from authentication.parser import data
  File "/home/souvik/PycharmProjects/ServiceHandler/authentication/parser.py", line 14, in <module>
    data = parser.parse_args()
  File "/home/souvik/utorapp/lib/python3.5/site-packages/flask_restful/reqparse.py", line 302, in parse_args
    req.unparsed_arguments = dict(self.argument_class('').source(req)) if strict else {}
  File "/home/souvik/utorapp/lib/python3.5/site-packages/werkzeug/local.py", line 364, in <lambda>
    __setattr__ = lambda x, n, v: setattr(x._get_current_object(), n, v)
  File "/home/souvik/utorapp/lib/python3.5/site-packages/werkzeug/local.py", line 306, in _get_current_object
    return self.__local()
  File "/home/souvik/utorapp/lib/python3.5/site-packages/flask/globals.py", line 37, in _lookup_req_object
    raise RuntimeError(_request_ctx_err_msg)
RuntimeError: Working outside of request context.

This typically means that you attempted to use functionality that needed
an active HTTP request.  Consult the documentation on testing for
information about how to avoid this problem.

Solution

You currently call data = parser.parse_args() in top-level code of a module. This runs at import time, but there is nothing to parse while your module gets imported, since this happens during startup and not while handling a request.

Call this from your view function (ie the code that runs while handling a request) instead. You will also need to restructure your code - calling api.add_resource() is something you do during startup/initialization time, not while handling a request.

The important thing to understand is that this is not PHP where all your code runs when a request is received. Instead, the Python modules are imported when you start your application (flask run, app.run(), or running it in a WSGI container). When a request is received only the code related to handling that request runs.