from pytube import YouTube
import os
yt = YouTube(str(input("Enter URL of youtube video: \n ")))
video = yt.streams.filter(only_audio=True).first()
print("Enter the destination address (leave blank to save in current directory)")
destination = str(input(" ")) or '.'
out_file = video.download(output_path=destination)
base, ext = os.path.splitext(out_file)
new_file = base + '.mp3'
os.rename(out_file, new_file)
print(yt.title + " has been successfully downloaded.")