Token POST is not callable??

I am using Python 3.6, with Pycharm Community

I am trying to get a Token but keep getting object is not callable error?? I would appreciate any pointers to resolve this..

The error points at the line below,  the error msg = TypeError: 'str' object is not callable

req = urllib.request("POST"(tokenURL, urlencode(params)))

#### For Python 3
import os, sys
import ssl
import json

import urllib
import urllib.request
from urllib.request import urlopen
from urllib.parse import urlencode
from urllib.parse import urlparse
import http.client
import requests

params = {'f': 'pjson', 'username': username, 'password': password, 'referer': referer}

#For Python 3
req = urllib.request("POST"(tokenURL, urlencode(params)))
response = urllib.parse.urlopen(req)


try:
    response = urllib.urlopen(req)
except:
    gcontext = ssl.SSLContext(ssl.PROTOCOL_TLSv1)
    response = urllib.urlopen(req, context=gcontext)
data = json.load(response)
token = data['token']
print(token)