import subprocess
import time

time_to_wait = 500
url = ""


command = """youtube-dl --download-archive downloaded.txt --no-post-overwrites -f bestvideo+bestaudio -i -o %(playlist_index)s-%(title)s.%(ext)s""" + " {}".format(url)

while True:

    subprocess.run(command)
    time.sleep(time_to_wait)