download only audio from youtube using youtube-dl python

import subprocess

process = subprocess.Popen(['youtube-dl',  '-f','bestaudio','https://www.youtube.com/watch?v=dCsr0CNqB3g' ],
                        stdout=subprocess.PIPE,
                        )
while True:
    output = process.stdout.readline()
    if output == '' and process.poll() is not None:
        break    if output:
        print(output.strip())
    rc = process.poll()