returns a list of 'Unassigned' ports from iana.org

ports.py

import os.path
from csv import reader as csvreader
import json, requests, logging

# url for retieving the unregistered portlist
IANAURL = 'http://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.csv'

def getAvailPorts(minport=1024):
    """
    Downloads the current iana.org port assignment csv
    Sorts the list for 'Unassigned'
    saves the port list in JSON to a local file
    returns a list of 'Unassigned' ports
    """
    # check if we have a saved port list
    if os.path.isfile('ports.json'):
        with open('ports.json') as f:
            portList = json.load(f)
            return portList
    # download the list
    else:
        logging.info("Downloading: '%s'" % IANAURL)
        logging.info("This could take awhile...")
        raw = requests.get(IANAURL)
        reader = csvreader(raw.iter_lines(), delimiter=',')
        portList = []
        logging.info("Generating portList...")
        for row in reader:
            if 'Unassigned' in row:
                if '-' in row[1]: # if port range
                    if int(row[1].split('-')[0]) > minport:
                        for i in range(
                                int(row[1].split('-')[0]),
                                int(row[1].split('-')[1])
                                ):
                            portList.append(i)
                elif int(row[1]) > minport:
                    portList.append(int(row[1]))
        logging.info("Found %s 'Unassigned' ports > %s" % (
                str(len(portList)), str(minport))
                )
        with open('ports.json', 'w+') as f:
            json.dump(portList, f, sort_keys=True, indent=4, ensure_ascii=False)
        return portList

if __name__ == "__main__":
    logging.basicConfig()
    getAvailPorts()