Subscript system of one Youtube channel using youtube-dl that only downloads newer videos since last time ran. youtube-dl can be found at http://rg3.github.io/youtube-dl/

subscribe_youtube.py

from datetime import date, datetime
from subprocess import Popen, PIPE
import sys

DATEFORMAT = "%Y%m%d"
CONFPATH = 'last_updated.txt'
CMD = '''\
youtube-dl.exe -ci -w -o "%(title)s.%(ext)s" http://www.youtube.com/user/WTii1 --match-title "Warcraft 3.*"\
'''


def ytdl():
	global DATEFORMAT,CONFPATH,CMD
	last_updated = None

	try:
		with open(CONFPATH, "r") as conf:
			last_updated = datetime.strptime(conf.readline().strip(), DATEFORMAT)
	except:
		last_updated = date.today()
		print "No config file found! Picking only today"

	CMD += " --dateafter %s" % last_updated.strftime(DATEFORMAT)

	print "Executing %s" % CMD

	process = Popen(CMD, shell=True ,stdout=PIPE, stderr=PIPE)
	# This does not show progressbar while downloading
	# for line in iter(process.stdout.readline, ''): print line,
	# instead, loop each character

	while True:
		out = process.stdout.read(1)
		if out == '' and process.poll() != None:
			break
		if out != '':
			sys.stdout.write(out)
			sys.stdout.flush()

	print "Saving config"

	with open(CONFPATH, "w") as conf:
		conf.write(date.today().strftime(DATEFORMAT))

if __name__ == "__main__":
	ytdl()

Made this built for youtube-dl and a pull request but instead a better solution was built by them. See the --download-archive option.