hn.py

import feedparser
from Pubnub import Pubnub
import time
from argparse import ArgumentParser
import sys


def current_hn(rss):
    return feedparser.parse(rss)

def create_message(rss):
    message = []
    for index, entry in enumerate(rss.entries):
        post = {}
        post["rank"] = index + 1
        post["title"] = entry.title
        post["link"] = entry.link
        post["comments"] = entry.comments
        message.append(post)
    return message

def publish(pubnub, message):
    pubnub.publish({
        "channel": "hacker-news",
        "message": message
    })

def check_for_change(mode, hn, rss):
    new_hn = current_hn(rss)
    if mode == "entire":
        if str(new_hn) != str(hn):
            return create_message(new_hn)
    elif mode == "new":
        new_hn = create_message(new_hn)
        hn = create_message(hn)
        hn_titles = []
        [hn_titles.append(topic["title"]) for topic in hn]
        message = []
        for new_title in new_hn:
            if new_title["title"] not in hn_titles:
                message.append(new_title)
        return message 
    else:
        return None


if __name__ == "__main__":
    parser = ArgumentParser(description="Options to parse RSS Feed")
    parser.add_argument("-r", "--rsslink", dest="rss_link", type=str, default="https://news.ycombinator.com/rss", help="This is a link to the rss feed desired to scrape.")
    parser.add_argument("-t", "--time", dest="time_to_wait", type=int, default=10, help="In seconds how long do you want to wait between checking the rss feed.")
    parser.add_argument("-m", "--mode", dest="mode", type=str, default="entire", help="Set the mode in which to poll for feeds. Either 'entire' which will publish an entire new feed every update. Or 'new' which will only pulish new changes.")

    argv = sys.argv[1:]
    try:
        argp = parser.parse_args(argv)
    except SystemExit as ex:
        print("Eception when parsing args because of => " + str(ex))
        sys.exit()

    try:
        rss_link = argp.rss_link
        time_to_wait = argp.time_to_wait
        mode = argp.mode
    except Exception as ex:
        print("Something went wrong because of => " + str(ex))

    pubnub = Pubnub("demo", "demo")
    fp = current_hn(rss_link)

    while True:
        message = check_for_change(mode, fp, rss_link)
        if message is not None:
            publish(pubnub, message)
            fp = current_hn(rss_link)
        time.sleep(time_to_wait)