mp4 to mp3 in python

# -*- coding: utf-8 -*-
from moviepy.editor import *

video = VideoFileClip('Sora no Kiseki the 3rd Evolution [BGM RIP] - Cry for your Eternity.mp4')
video.audio.write_audiofile('test.mp3')

import os
from moviepy.editor import *
video = VideoFileClip(os.path.join("path","to","movie.mp4"))
video.audio.write_audiofile(os.path.join("path","to","movie_sound.mp3"))