I have this python code:
import os
os.system('cd C:\yt')
os.system("ffmpeg.exe -i test.mp4 newfilename.mp3")
'ffmpeg.exe' is not recognized as an internal or external command,
operable program or batch file.
You need to move to that directory. Try the following:
import os
os.chdir('C:\yt')
print os.getcwd() # confirm location
os.system("ffmpeg.exe -i test.mp4 newfilename.mp3")